Oracle 10g sql fundamentals i

Oracle Database 10g: SQL Fundamentals I Electronic Presentation D17108GC11 Production 1.1 August 2004 D39769 ®

Author Copyright © 2004, Oracle. All rights reserved. Nancy Greenberg This documentation contains proprietary information of Oracle Corporation. It is provided under a license agreement containing restrictions on use and disclosure and is also protected by copyright law. Reverse engineering of the software is prohibited. If this documentation is delivered to a U.S. Technical Contributors Government Agency of the Department of Defense, then it is delivered with Restricted Rights and the and Reviewers following legend is applicable: Wayne Abbott Restricted Rights Legend Christian Bauwens Perry Benson Use, duplication or disclosure by the Government is subject to restrictions for commercial computer software and shall be deemed to be Restricted Rights software under Federal law, as set forth in Brian Boxx subparagraph (c)(1)(ii) of DFARS 252.227-7013, Rights in Technical Data and Computer Software Zarko Cesljas (October 1988). Dairy Chan Laszlo Czinkoczki This material or any portion of it may not be copied in any form or by any means without the express Marjolein Dekkers prior written permission of Oracle Corporation. Any other copying is a violation of copyright law and Matthew Gregory may result in civil and/or criminal penalties. Stefan Grenstad If this documentation is delivered to a U.S. Government Agency not within the Department of Joel Goodman Defense, then it is delivered with “Restricted Rights,” as defined in FAR 52.227-14, Rights in Data- Rosita Hanoman General, including Alternate III (June 1987). Sushma Jagannath Angelika Krupp The information in this document is subject to change without notice. If you find any problems in the Christopher Lawless documentation, please report them in writing to Education Products, Oracle Corporation, 500 Oracle Marcelo Manzano Parkway, Box SB-6, Redwood Shores, CA 94065. Oracle Corporation does not warrant that this Isabelle Marchand document is error-free. Malika Marghadi Oracle and all references to Oracle products are trademarks or registered trademarks of Oracle Valli Pataballa Corporation. Elspeth Payne Ligia Jasmin Robayo All other products or company names are used for identification purposes only, and may be Bryan Roberts trademarks of their respective owners. Helen Robertson Lata Shivaprasad John Soltani Priya Vennapusa Ken Woolfe Publisher Jobi Varghese

Lesson Objectives After completing this lesson, you should be able to do the following: • List the features of Oracle10g • Discuss the theoretical and physical aspects of a relational database • Describe the Oracle implementation of the RDBMS and ORDBMS • Understand the goals of the course Copyright © 2004, Oracle. All rights reserved.

Goals of the Course After completing this course, you should be able to do the following: • Identify the major structural components of Oracle Database 10g • Retrieve row and column data from tables with the SELECT statement • Create reports of sorted and restricted data • Employ SQL functions to generate and retrieve customized data • Run data manipulation language (DML) statements to update data in Oracle Database 10g • Obtain metadata by querying the dictionary views Copyright © 2004, Oracle. All rights reserved.

Relational and Object Relational Database Management Systems • Relational model and object relational model • User-defined data types and objects • Fully compatible with relational database • Support of multimedia and large objects • High-quality database server features Copyright © 2004, Oracle. All rights reserved.

Oracle Internet Platform Clients Any Any Any browser mail client FTP client Development tools System management Internet applications SQL Business logic Presentation and and data business logic PL/SQL Databases Application servers Java Network services Copyright © 2004, Oracle. All rights reserved.

Relational Database Concept • Dr. E. F. Codd proposed the relational model for database systems in 1970. • It is the basis for the relational database management system (RDBMS). • The relational model consists of the following: – Collection of objects or relations – Set of operators to act on the relations – Data integrity for accuracy and consistency Copyright © 2004, Oracle. All rights reserved.

Definition of a Relational Database A relational database is a collection of relations or two-dimensional tables. Oracle server Table name: EMPLOYEES Table name: DEPARTMENTS … … Copyright © 2004, Oracle. All rights reserved.

Entity Relationship Model • Create an entity relationship diagram from business specifications or narratives: EMPLOYEE DEPARTMENT assigned to #* number #* number * name * name o job title composed of o location • Scenario – “. . . Assign one or more employees to a department . . .” – “. . . Some departments do not yet have assigned employees . . .” Copyright © 2004, Oracle. All rights reserved.

Entity Relationship Modeling Conventions Entity Attribute • Singular, unique name • Singular name • Uppercase • Lowercase • Soft box • Mandatory marked with * • Synonym in parentheses • Optional marked with “o” EMPLOYEE DEPARTMENT #* number assigned to #* number * name * name o job title composed of o location Unique identifier (UID) Primary marked with “#” Secondary marked with “(#)” Copyright © 2004, Oracle. All rights reserved.

Relating Multiple Tables • Each row of data in a table is uniquely identified by a primary key (PK). • You can logically relate data from multiple tables using foreign keys (FK). Table name: DEPARTMENTS Table name: EMPLOYEES … Primary key Foreign key Primary key Copyright © 2004, Oracle. All rights reserved.

Relational Database Properties A relational database: • Can be accessed and modified by executing structured query language (SQL) statements • Contains a collection of tables with no physical pointers • Uses a set of operators Copyright © 2004, Oracle. All rights reserved.

Communicating with an RDBMS Using SQL SQL statement is entered. Statement is sent to Oracle server. SELECT department_name FROM departments; Oracle server Copyright © 2004, Oracle. All rights reserved.

SQL Statements SELECT INSERT UPDATE Data manipulation language (DML) DELETE MERGE CREATE ALTER DROP Data definition language (DDL) RENAME TRUNCATE COMMENT GRANT Data control language (DCL) REVOKE COMMIT ROLLBACK Transaction control SAVEPOINT Copyright © 2004, Oracle. All rights reserved.

Summary • Oracle Database 10g is the database for grid computing. • The database is based on the object relational database management system. • Relational databases are composed of relations, managed by relational operations, and governed by data integrity constraints. • With the Oracle server, you can store and manage information by using the SQL language and PL/SQL engine. Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • List the capabilities of SQL SELECT statements • Execute a basic SELECT statement • Differentiate between SQL statements and iSQL*Plus commands Copyright © 2004, Oracle. All rights reserved.

Basic SELECT Statement SELECT *|{[DISTINCT] column|expression [alias],...} FROM table; • SELECT identifies the columns to be displayed • FROM identifies the table containing those columns Copyright © 2004, Oracle. All rights reserved.

Writing SQL Statements • SQL statements are not case-sensitive. • SQL statements can be on one or more lines. • Keywords cannot be abbreviated or split across lines. • Clauses are usually placed on separate lines. • Indents are used to enhance readability. • In iSQL*Plus, SQL statements can optionally be terminated by a semicolon (;). Semicolons are required if you execute multiple SQL statements. • In SQL*plus, you are required to end each SQL statement with a semicolon (;). Copyright © 2004, Oracle. All rights reserved.

Column Heading Defaults • iSQL*Plus: – Default heading alignment: Center – Default heading display: Uppercase • SQL*Plus: – Character and Date column headings are left- aligned – Number column headings are right-aligned – Default heading display: Uppercase Copyright © 2004, Oracle. All rights reserved.

Arithmetic Expressions Create expressions with number and date data by using arithmetic operators. Operator Description + Add - Subtract * Multiply / Divide Copyright © 2004, Oracle. All rights reserved.

Defining a Null Value • A null is a value that is unavailable, unassigned, unknown, or inapplicable. • A null is not the same as a zero or a blank space. SELECT last_name, job_id, salary, commission_pct FROM employees; … … Copyright © 2004, Oracle. All rights reserved.

Null Values in Arithmetic Expressions Arithmetic expressions containing a null value evaluate to null. SELECT last_name, 12*salary*commission_pct FROM employees; … … Copyright © 2004, Oracle. All rights reserved.

Defining a Column Alias A column alias: • Renames a column heading • Is useful with calculations • Immediately follows the column name (There can also be the optional AS keyword between the column name and alias.) • Requires double quotation marks if it contains spaces or special characters or if it is case- sensitive Copyright © 2004, Oracle. All rights reserved.

Using Column Aliases SELECT last_name AS name, commission_pct comm FROM employees; … SELECT last_name "Name" , salary*12 "Annual Salary" FROM employees; … Copyright © 2004, Oracle. All rights reserved.

Concatenation Operator A concatenation operator: • Links columns or character strings to other columns • Is represented by two vertical bars (||) • Creates a resultant column that is a character expression SELECT last_name||job_id AS "Employees" FROM employees; … Copyright © 2004, Oracle. All rights reserved.

Literal Character Strings • A literal is a character, a number, or a date that is included in the SELECT statement. • Date and character literal values must be enclosed by single quotation marks. • Each character string is output once for each row returned. Copyright © 2004, Oracle. All rights reserved.

Alternative Quote (q) Operator • Specify your own quotation mark delimiter • Choose any delimiter • Increase readability and usability SELECT department_name || q'[, it's assigned Manager Id: ]' || manager_id AS "Department and Manager" FROM departments; … Copyright © 2004, Oracle. All rights reserved.

Duplicate Rows The default display of queries is all rows, including duplicate rows. SELECT department_id FROM employees; 1 … SELECT DISTINCT department_id FROM employees; 2 … Copyright © 2004, Oracle. All rights reserved.

SQL Statements Versus iSQL*Plus Commands SQL iSQL*Plus • A language • An environment • ANSI standard • Oracle-proprietary • Keyword cannot be • Keywords can be abbreviated abbreviated • Statements manipulate • Commands do not allow data and table definitions manipulation of values in in the database the database • Runs on a browser • Centrally loaded; does not have to be implemented on each machine SQL iSQL*Plus statements commands Copyright © 2004, Oracle. All rights reserved.

Overview of iSQL*Plus After you log in to iSQL*Plus, you can: • Describe table structures • Enter, execute, and edit SQL statements • Save or append SQL statements to files • Execute or edit statements that are stored in saved script files Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Write a SELECT statement that: – Returns all rows and columns from a table – Returns specified columns from a table – Uses column aliases to display more descriptive column headings • Use the iSQL*Plus environment to write, save, and execute SQL statements and iSQL*Plus commands SELECT *|{[DISTINCT] column|expression [alias],...} FROM table; Copyright © 2004, Oracle. All rights reserved.

Practice 1: Overview This practice covers the following topics: • Selecting all data from different tables • Describing the structure of tables • Performing arithmetic calculations and specifying column names • Using iSQL*Plus Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Limit the rows that are retrieved by a query • Sort the rows that are retrieved by a query • Use ampersand substitution in iSQL*Plus to restrict and sort output at run time Copyright © 2004, Oracle. All rights reserved.

Limiting the Rows That Are Selected • Restrict the rows that are returned by using the WHERE clause: SELECT *|{[DISTINCT] column|expression [alias],...} FROM table [WHERE condition(s)]; • The WHERE clause follows the FROM clause. Copyright © 2004, Oracle. All rights reserved.

Character Strings and Dates • Character strings and date values are enclosed by single quotation marks. • Character values are case-sensitive, and date values are format-sensitive. • The default date format is DD-MON-RR. SELECT last_name, job_id, department_id FROM employees WHERE last_name = 'Whalen' ; Copyright © 2004, Oracle. All rights reserved.

Comparison Conditions Operator Meaning = Equal to > Greater than >= Greater than or equal to < Less than <= Less than or equal to <> Not equal to BETWEEN Between two values ...AND... (inclusive) IN(set) Match any of a list of values LIKE Match a character pattern IS NULL Is a null value Copyright © 2004, Oracle. All rights reserved.

Using the BETWEEN Condition Use the BETWEEN condition to display rows based on a range of values: SELECT last_name, salary FROM employees WHERE salary BETWEEN 2500 AND 3500 ; Lower limit Upper limit Copyright © 2004, Oracle. All rights reserved.

Using the IN Condition Use the IN membership condition to test for values in a list: SELECT employee_id, last_name, salary, manager_id FROM employees WHERE manager_id IN (100, 101, 201) ; Copyright © 2004, Oracle. All rights reserved.

Using the LIKE Condition • Use the LIKE condition to perform wildcard searches of valid search string values. • Search conditions can contain either literal characters or numbers: – % denotes zero or many characters. – _ denotes one character. SELECT first_name FROM employees WHERE first_name LIKE 'S%' ; Copyright © 2004, Oracle. All rights reserved.

Using the LIKE Condition • You can combine pattern-matching characters: SELECT last_name FROM employees WHERE last_name LIKE '_o%' ; • You can use the ESCAPE identifier to search for the actual % and _ symbols. Copyright © 2004, Oracle. All rights reserved.

Logical Conditions Operator Meaning AND Returns TRUE if both component conditions are true OR Returns TRUE if either component condition is true NOT Returns TRUE if the following condition is false Copyright © 2004, Oracle. All rights reserved.

Using the AND Operator AND requires both conditions to be true: SELECT employee_id, last_name, job_id, salary FROM employees WHERE salary >=10000 AND job_id LIKE '%MAN%' ; Copyright © 2004, Oracle. All rights reserved.

Using the OR Operator OR requires either condition to be true: SELECT employee_id, last_name, job_id, salary FROM employees WHERE salary >= 10000 OR job_id LIKE '%MAN%' ; Copyright © 2004, Oracle. All rights reserved.

Rules of Precedence Operator Meaning 1 Arithmetic operators 2 Concatenation operator 3 Comparison conditions 4 IS [NOT] NULL, LIKE, [NOT] IN 5 [NOT] BETWEEN 6 Not equal to 7 NOT logical condition 8 AND logical condition 9 OR logical condition You can use parentheses to override rules of precedence. Copyright © 2004, Oracle. All rights reserved.

Rules of Precedence SELECT last_name, job_id, salary FROM employees WHERE job_id = 'SA_REP' 1 OR job_id = 'AD_PRES' AND salary > 15000; SELECT last_name, job_id, salary FROM employees WHERE (job_id = 'SA_REP' 2 OR job_id = 'AD_PRES') AND salary > 15000; Copyright © 2004, Oracle. All rights reserved.

Using the ORDER BY Clause • Sort retrieved rows with the ORDER BY clause: – ASC: ascending order, default – DESC: descending order • The ORDER BY clause comes last in the SELECT statement: SELECT last_name, job_id, department_id, hire_date FROM employees ORDER BY hire_date ; … Copyright © 2004, Oracle. All rights reserved.

Sorting • Sorting in descending order: SELECT last_name, job_id, department_id, hire_date FROM employees ORDER BY hire_date DESC ; 1 • Sorting by column alias: SELECT employee_id, last_name, salary*12 annsal FROM employees 2 ORDER BY annsal ; • Sorting by multiple columns: SELECT last_name, department_id, salary FROM employees 3 ORDER BY department_id, salary DESC; Copyright © 2004, Oracle. All rights reserved.

Substitution Variables • Use iSQL*Plus substitution variables to: – Temporarily store values with single-ampersand (&) and double-ampersand (&&) substitution • Use substitution variables to supplement the following: – WHERE conditions – ORDER BY clauses – Column expressions – Table names – Entire SELECT statements Copyright © 2004, Oracle. All rights reserved.

Using the & Substitution Variable Use a variable prefixed with an ampersand (&) to prompt the user for a value: SELECT employee_id, last_name, salary, department_id FROM employees WHERE employee_id = &employee_num ; Copyright © 2004, Oracle. All rights reserved.

Character and Date Values with Substitution Variables Use single quotation marks for date and character values: SELECT last_name, department_id, salary*12 FROM employees WHERE job_id = '&job_title' ; Copyright © 2004, Oracle. All rights reserved.

Specifying Column Names, Expressions, and Text SELECT employee_id, last_name, job_id,&column_name FROM employees WHERE &condition ORDER BY &order_column ; salary salary > 15000 last_name Copyright © 2004, Oracle. All rights reserved.

Using the && Substitution Variable Use the double ampersand (&&) if you want to reuse the variable value without prompting the user each time: SELECT employee_id, last_name, job_id, &&column_name FROM employees ORDER BY &column_name ; … Copyright © 2004, Oracle. All rights reserved.

Using the iSQL*Plus DEFINE Command • Use the iSQL*Plus DEFINE command to create and assign a value to a variable. • Use the iSQL*Plus UNDEFINE command to remove a variable. DEFINE employee_num = 200 SELECT employee_id, last_name, salary, department_id FROM employees WHERE employee_id = &employee_num ; UNDEFINE employee_num Copyright © 2004, Oracle. All rights reserved.

Using the VERIFY Command Use the VERIFY command to toggle the display of the substitution variable, both before and after iSQL*Plus replaces substitution variables with values: SET VERIFY ON SELECT employee_id, last_name, salary, department_id FROM employees WHERE employee_id = &employee_num; old 3: WHERE employee_id = &employee_num new 3: WHERE employee_id = 200 Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Use the WHERE clause to restrict rows of output: – Use the comparison conditions – Use the BETWEEN, IN, LIKE, and NULL conditions – Apply the logical AND, OR, and NOT operators • Use the ORDER BY clause to sort rows of output: SELECT *|{[DISTINCT] column|expression [alias],...} FROM table [WHERE condition(s)] [ORDER BY {column, expr, alias} [ASC|DESC]] ; • Use ampersand substitution in iSQL*Plus to restrict and sort output at run time Copyright © 2004, Oracle. All rights reserved.

Practice 2: Overview This practice covers the following topics: • Selecting data and changing the order of the rows that are displayed • Restricting rows by using the WHERE clause • Sorting rows by using the ORDER BY clause • Using substitution variables to add flexibility to your SQL SELECT statements Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Describe various types of functions that are available in SQL • Use character, number, and date functions in SELECT statements • Describe the use of conversion functions Copyright © 2004, Oracle. All rights reserved.

Single-Row Functions Single-row functions: • Manipulate data items • Accept arguments and return one value • Act on each row that is returned • Return one result per row • May modify the data type • Can be nested • Accept arguments that can be a column or an expression function_name [(arg1, arg2,...)] Copyright © 2004, Oracle. All rights reserved.

Character Functions Character functions Case-manipulation Character-manipulation functions functions LOWER CONCAT UPPER SUBSTR INITCAP LENGTH INSTR LPAD | RPAD TRIM REPLACE Copyright © 2004, Oracle. All rights reserved.

Case-Manipulation Functions These functions convert case for character strings: Function Result LOWER('SQL Course') sql course UPPER('SQL Course') SQL COURSE INITCAP('SQL Course') Sql Course Copyright © 2004, Oracle. All rights reserved.

Using Case-Manipulation Functions Display the employee number, name, and department number for employee Higgins: SELECT employee_id, last_name, department_id FROM employees WHERE last_name = 'higgins'; no rows selected SELECT employee_id, last_name, department_id FROM employees WHERE LOWER(last_name) = 'higgins'; Copyright © 2004, Oracle. All rights reserved.

Character-Manipulation Functions These functions manipulate character strings: Function Result CONCAT('Hello', 'World') HelloWorld SUBSTR('HelloWorld',1,5) Hello LENGTH('HelloWorld') 10 INSTR('HelloWorld', 'W') 6 LPAD(salary,10,'*') *****24000 RPAD(salary, 10, '*') 24000***** REPLACE BLACK and BLUE ('JACK and JUE','J','BL') TRIM('H' FROM 'HelloWorld') elloWorld Copyright © 2004, Oracle. All rights reserved.

Using the Character-Manipulation Functions 1 SELECT employee_id, CONCAT(first_name, last_name) NAME, job_id, LENGTH (last_name), 2 INSTR(last_name, 'a') "Contains 'a'?" FROM employees 3 WHERE SUBSTR(job_id, 4) = 'REP'; 1 2 3 Copyright © 2004, Oracle. All rights reserved.

Number Functions • ROUND: Rounds value to specified decimal • TRUNC: Truncates value to specified decimal • MOD: Returns remainder of division Function Result ROUND(45.926, 2) 45.93 TRUNC(45.926, 2) 45.92 MOD(1600, 300) 100 Copyright © 2004, Oracle. All rights reserved.

Using the ROUND Function 1 2 SELECT ROUND(45.923,2), ROUND(45.923,0), ROUND(45.923,-1) 3 FROM DUAL; 1 2 3 DUAL is a dummy table that you can use to view results from functions and calculations. Copyright © 2004, Oracle. All rights reserved.

Using the MOD Function For all employees with job title of Sales Representative, calculate the remainder of the salary after it is divided by 5,000. SELECT last_name, salary, MOD(salary, 5000) FROM employees WHERE job_id = 'SA_REP'; Copyright © 2004, Oracle. All rights reserved.

Working with Dates • The Oracle database stores dates in an internal numeric format: century, year, month, day, hours, minutes, and seconds. • The default date display format is DD-MON-RR. – Enables you to store 21st-century dates in the 20th century by specifying only the last two digits of the year – Enables you to store 20th-century dates in the 21st century in the same way SELECT last_name, hire_date FROM employees WHERE hire_date < '01-FEB-88'; Copyright © 2004, Oracle. All rights reserved.

Arithmetic with Dates • Add or subtract a number to or from a date for a resultant date value. • Subtract two dates to find the number of days between those dates. • Add hours to a date by dividing the number of hours by 24. Copyright © 2004, Oracle. All rights reserved.

Date Functions Function Result MONTHS_BETWEEN Number of months between two dates ADD_MONTHS Add calendar months to date NEXT_DAY Next day of the date specified LAST_DAY Last day of the month ROUND Round date TRUNC Truncate date Copyright © 2004, Oracle. All rights reserved.

Using Date Functions Function Result MONTHS_BETWEEN 19.6774194 ('01-SEP-95','11-JAN-94') ADD_MONTHS ('11-JAN-94',6) '11-JUL-94' NEXT_DAY ('01-SEP-95','FRIDAY') '08-SEP-95' LAST_DAY ('01-FEB-95') '28-FEB-95' Copyright © 2004, Oracle. All rights reserved.

Using Date Functions Assume SYSDATE = '25-JUL-03': Function Result ROUND(SYSDATE,'MONTH') 01-AUG-03 ROUND(SYSDATE ,'YEAR') 01-JAN-04 TRUNC(SYSDATE ,'MONTH') 01-JUL-03 TRUNC(SYSDATE ,'YEAR') 01-JAN-03 Copyright © 2004, Oracle. All rights reserved.

Practice 3: Overview of Part 1 This practice covers the following topics: • Writing a query that displays the current date • Creating queries that require the use of numeric, character, and date functions • Performing calculations of years and months of service for an employee Copyright © 2004, Oracle. All rights reserved.

Implicit Data Type Conversion For assignments, the Oracle server can automatically convert the following: From To VARCHAR2 or CHAR NUMBER VARCHAR2 or CHAR DATE NUMBER VARCHAR2 DATE VARCHAR2 Copyright © 2004, Oracle. All rights reserved.

Implicit Data Type Conversion For expression evaluation, the Oracle Server can automatically convert the following: From To VARCHAR2 or CHAR NUMBER VARCHAR2 or CHAR DATE Copyright © 2004, Oracle. All rights reserved.

Using the TO_CHAR Function with Dates TO_CHAR(date, 'format_model') The format model: • Must be enclosed by single quotation marks • Is case-sensitive • Can include any valid date format element • Has an fm element to remove padded blanks or suppress leading zeros • Is separated from the date value by a comma Copyright © 2004, Oracle. All rights reserved.

Elements of the Date Format Model Element Result YYYY Full year in numbers YEAR Year spelled out (in English) MM Two-digit value for month MONTH Full name of the month MON Three-letter abbreviation of the month DY Three-letter abbreviation of the day of the week DAY Full name of the day of the week DD Numeric day of the month Copyright © 2004, Oracle. All rights reserved.

Elements of the Date Format Model • Time elements format the time portion of the date: HH24:MI:SS AM 15:45:32 PM • Add character strings by enclosing them in double quotation marks: DD "of" MONTH 12 of OCTOBER • Number suffixes spell out numbers: ddspth fourteenth Copyright © 2004, Oracle. All rights reserved.

Using the TO_CHAR Function with Numbers TO_CHAR(number, 'format_model') These are some of the format elements that you can use with the TO_CHAR function to display a number value as a character: Element Result 9 Represents a number 0 Forces a zero to be displayed $ Places a floating dollar sign L Uses the floating local currency symbol . Prints a decimal point , Prints a comma as thousands indicator Copyright © 2004, Oracle. All rights reserved.

Using the TO_NUMBER and TO_DATE Functions • Convert a character string to a number format using the TO_NUMBER function: TO_NUMBER(char[, 'format_model']) • Convert a character string to a date format using the TO_DATE function: TO_DATE(char[, 'format_model']) • These functions have an fx modifier. This modifier specifies the exact matching for the character argument and date format model of a TO_DATE function. Copyright © 2004, Oracle. All rights reserved.

RR Date Format Current Year Specified Date RR Format YY Format 1995 27-OCT-95 1995 1995 1995 27-OCT-17 2017 1917 2001 27-OCT-17 2017 2017 2001 27-OCT-95 1995 2095 If the specified two-digit year is: 0–49 50–99 If two digits The return date is in The return date is in of the 0–49 the current century the century before current the current one year are: The return date is in The return date is in 50–99 the century after the current century the current one Copyright © 2004, Oracle. All rights reserved.

Example of RR Date Format To find employees hired prior to 1990, use the RR date format, which produces the same results whether the command is run in 1999 or now: SELECT last_name, TO_CHAR(hire_date, 'DD-Mon-YYYY') FROM employees WHERE hire_date < TO_DATE('01-Jan-90','DD-Mon-RR'); Copyright © 2004, Oracle. All rights reserved.

Nesting Functions • Single-row functions can be nested to any level. • Nested functions are evaluated from deepest level to the least deep level. F3(F2(F1(col,arg1),arg2),arg3) Step 1 = Result 1 Step 2 = Result 2 Step 3 = Result 3 Copyright © 2004, Oracle. All rights reserved.

General Functions The following functions work with any data type and pertain to using nulls: • NVL (expr1, expr2) • NVL2 (expr1, expr2, expr3) • NULLIF (expr1, expr2) • COALESCE (expr1, expr2, ..., exprn) Copyright © 2004, Oracle. All rights reserved.

NVL Function Converts a null value to an actual value: • Data types that can be used are date, character, and number. • Data types must match: – NVL(commission_pct,0) – NVL(hire_date,'01-JAN-97') – NVL(job_id,'No Job Yet') Copyright © 2004, Oracle. All rights reserved.

Using the NVL Function SELECT last_name, salary, NVL(commission_pct, 0), 1 (salary*12) + (salary*12*NVL(commission_pct, 0)) AN_SAL FROM employees; 2 … 1 2 Copyright © 2004, Oracle. All rights reserved.

Using the NVL2 Function SELECT last_name, salary, commission_pct, 1 NVL2(commission_pct, 'SAL+COMM', 'SAL') income 2 FROM employees WHERE department_id IN (50, 80); 1 2 Copyright © 2004, Oracle. All rights reserved.

Using the NULLIF Function 1 SELECT first_name, LENGTH(first_name) "expr1", last_name, LENGTH(last_name) "expr2", 2 NULLIF(LENGTH(first_name), LENGTH(last_name)) result 3 FROM employees; … 1 2 3 Copyright © 2004, Oracle. All rights reserved.

Using the COALESCE Function • The advantage of the COALESCE function over the NVL function is that the COALESCE function can take multiple alternate values. • If the first expression is not null, the COALESCE function returns that expression; otherwise, it does a COALESCE of the remaining expressions. Copyright © 2004, Oracle. All rights reserved.

CASE Expression Facilitates conditional inquiries by doing the work of an IF-THEN-ELSE statement: CASE expr WHEN comparison_expr1 THEN return_expr1 [WHEN comparison_expr2 THEN return_expr2 WHEN comparison_exprn THEN return_exprn ELSE else_expr] END Copyright © 2004, Oracle. All rights reserved.

Using the CASE Expression Facilitates conditional inquiries by doing the work of an IF-THEN-ELSE statement: SELECT last_name, job_id, salary, CASE job_id WHEN 'IT_PROG' THEN 1.10*salary WHEN 'ST_CLERK' THEN 1.15*salary WHEN 'SA_REP' THEN 1.20*salary ELSE salary END "REVISED_SALARY" FROM employees; … … Copyright © 2004, Oracle. All rights reserved.

DECODE Function Facilitates conditional inquiries by doing the work of a CASE expression or an IF-THEN-ELSE statement: DECODE(col|expression, search1, result1 [, search2, result2,...,] [, default]) Copyright © 2004, Oracle. All rights reserved.

Using the DECODE Function SELECT last_name, job_id, salary, DECODE(job_id, 'IT_PROG', 1.10*salary, 'ST_CLERK', 1.15*salary, 'SA_REP', 1.20*salary, salary) REVISED_SALARY FROM employees; … … Copyright © 2004, Oracle. All rights reserved.

Using the DECODE Function Display the applicable tax rate for each employee in department 80: SELECT last_name, salary, DECODE (TRUNC(salary/2000, 0), 0, 0.00, 1, 0.09, 2, 0.20, 3, 0.30, 4, 0.40, 5, 0.42, 6, 0.44, 0.45) TAX_RATE FROM employees WHERE department_id = 80; Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Perform calculations on data using functions • Modify individual data items using functions • Manipulate output for groups of rows using functions • Alter date formats for display using functions • Convert column data types using functions • Use NVL functions • Use IF-THEN-ELSE logic Copyright © 2004, Oracle. All rights reserved.

Practice 3: Overview of Part 2 This practice covers the following topics: • Creating queries that require the use of numeric, character, and date functions • Using concatenation with functions • Writing case-insensitive queries to test the usefulness of character functions • Performing calculations of years and months of service for an employee • Determining the review date for an employee Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Identify the available group functions • Describe the use of group functions • Group data by using the GROUP BY clause • Include or exclude grouped rows by using the HAVING clause Copyright © 2004, Oracle. All rights reserved.

Using the AVG and SUM Functions You can use AVG and SUM for numeric data. SELECT AVG(salary), MAX(salary), MIN(salary), SUM(salary) FROM employees WHERE job_id LIKE '%REP%'; Copyright © 2004, Oracle. All rights reserved.

Using the MIN and MAX Functions You can use MIN and MAX for numeric, character, and date data types. SELECT MIN(hire_date), MAX(hire_date) FROM employees; Copyright © 2004, Oracle. All rights reserved.

Using the COUNT Function COUNT(*) returns the number of rows in a table: SELECT COUNT(*) 1 FROM employees WHERE department_id = 50; COUNT(expr) returns the number of rows with non- null values for the expr: SELECT COUNT(commission_pct) 2 FROM employees WHERE department_id = 80; Copyright © 2004, Oracle. All rights reserved.

Using the DISTINCT Keyword • COUNT(DISTINCT expr) returns the number of distinct non-null values of the expr. • To display the number of distinct department values in the EMPLOYEES table: SELECT COUNT(DISTINCT department_id) FROM employees; Copyright © 2004, Oracle. All rights reserved.

Group Functions and Null Values Group functions ignore null values in the column: SELECT AVG(commission_pct) 1 FROM employees; The NVL function forces group functions to include null values: SELECT AVG(NVL(commission_pct, 0)) 2 FROM employees; Copyright © 2004, Oracle. All rights reserved.

Creating Groups of Data: GROUP BY Clause Syntax SELECT column, group_function(column) FROM table [WHERE condition] [GROUP BY group_by_expression] [ORDER BY column]; You can divide rows in a table into smaller groups by using the GROUP BY clause. Copyright © 2004, Oracle. All rights reserved.

Using the GROUP BY Clause All columns in the SELECT list that are not in group functions must be in the GROUP BY clause. SELECT department_id, AVG(salary) FROM employees GROUP BY department_id ; Copyright © 2004, Oracle. All rights reserved.

Illegal Queries Using Group Functions Any column or expression in the SELECT list that is not an aggregate function must be in the GROUP BY clause: SELECT department_id, COUNT(last_name) FROM employees; SELECT department_id, COUNT(last_name) * ERROR at line 1: ORA-00937: not a single-group group function Column missing in the GROUP BY clause Copyright © 2004, Oracle. All rights reserved.

Illegal Queries Using Group Functions • You cannot use the WHERE clause to restrict groups. • You use the HAVING clause to restrict groups. • You cannot use group functions in the WHERE clause. SELECT department_id, AVG(salary) FROM employees WHERE AVG(salary) > 8000 GROUP BY department_id; WHERE AVG(salary) > 8000 * ERROR at line 3: ORA-00934: group function is not allowed here Cannot use the WHERE clause to restrict groups Copyright © 2004, Oracle. All rights reserved.

Restricting Group Results with the HAVING Clause When you use the HAVING clause, the Oracle server restricts groups as follows: 1. Rows are grouped. 2. The group function is applied. 3. Groups matching the HAVING clause are displayed. SELECT column, group_function FROM table [WHERE condition] [GROUP BY group_by_expression] [HAVING group_condition] [ORDER BY column]; Copyright © 2004, Oracle. All rights reserved.

Using the HAVING Clause SELECT job_id, SUM(salary) PAYROLL FROM employees WHERE job_id NOT LIKE '%REP%' GROUP BY job_id HAVING SUM(salary) > 13000 ORDER BY SUM(salary); Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Use the group functions COUNT, MAX, MIN, and AVG • Write queries that use the GROUP BY clause • Write queries that use the HAVING clause SELECT column, group_function FROM table [WHERE condition] [GROUP BY group_by_expression] [HAVING group_condition] [ORDER BY column]; Copyright © 2004, Oracle. All rights reserved.

Practice 4: Overview This practice covers the following topics: • Writing queries that use the group functions • Grouping by rows to achieve more than one result • Restricting groups by using the HAVING clause Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Write SELECT statements to access data from more than one table using equijoins and non- equijoins • Join a table to itself by using a self-join • View data that generally does not meet a join condition by using outer joins • Generate a Cartesian product of all rows from two or more tables Copyright © 2004, Oracle. All rights reserved.

Types of Joins Joins that are compliant with the SQL:1999 standard include the following: • Cross joins • Natural joins • USING clause • Full (or two-sided) outer joins • Arbitrary join conditions for outer joins Copyright © 2004, Oracle. All rights reserved.

Joining Tables Using SQL:1999 Syntax Use a join to query data from more than one table: SELECT table1.column, table2.column FROM table1 [NATURAL JOIN table2] | [JOIN table2 USING (column_name)] | [JOIN table2 ON (table1.column_name = table2.column_name)]| [LEFT|RIGHT|FULL OUTER JOIN table2 ON (table1.column_name = table2.column_name)]| [CROSS JOIN table2]; Copyright © 2004, Oracle. All rights reserved.

Creating Natural Joins • The NATURAL JOIN clause is based on all columns in the two tables that have the same name. • It selects rows from the two tables that have equal values in all matched columns. • If the columns having the same names have different data types, an error is returned. Copyright © 2004, Oracle. All rights reserved.

Creating Joins with the USING Clause • If several columns have the same names but the data types do not match, the NATURAL JOIN clause can be modified with the USING clause to specify the columns that should be used for an equijoin. • Use the USING clause to match only one column when more than one column matches. • Do not use a table name or alias in the referenced columns. • The NATURAL JOIN and USING clauses are mutually exclusive. Copyright © 2004, Oracle. All rights reserved.

Retrieving Records with the USING Clause SELECT employees.employee_id, employees.last_name, departments.location_id, department_id FROM employees JOIN departments USING (department_id) ; … Copyright © 2004, Oracle. All rights reserved.

Qualifying Ambiguous Column Names • Use table prefixes to qualify column names that are in multiple tables. • Use table prefixes to improve performance. • Use column aliases to distinguish columns that have identical names but reside in different tables. • Do not use aliases on columns that are identified in the USING clause and listed elsewhere in the SQL statement. Copyright © 2004, Oracle. All rights reserved.

Using Table Aliases • Use table aliases to simplify queries. • Use table aliases to improve performance. SELECT e.employee_id, e.last_name, d.location_id, department_id FROM employees e JOIN departments d USING (department_id) ; Copyright © 2004, Oracle. All rights reserved.

Creating Joins with the ON Clause • The join condition for the natural join is basically an equijoin of all columns with the same name. • Use the ON clause to specify arbitrary conditions or specify columns to join. • The join condition is separated from other search conditions. • The ON clause makes code easy to understand. Copyright © 2004, Oracle. All rights reserved.

Retrieving Records with the ON Clause SELECT e.employee_id, e.last_name, e.department_id, d.department_id, d.location_id FROM employees e JOIN departments d ON (e.department_id = d.department_id); … Copyright © 2004, Oracle. All rights reserved.

Applying Additional Conditions to a Join SELECT e.employee_id, e.last_name, e.department_id, d.department_id, d.location_id FROM employees e JOIN departments d ON (e.department_id = d.department_id) AND e.manager_id = 149 ; Copyright © 2004, Oracle. All rights reserved.

Creating Three-Way Joins with the ON Clause SELECT employee_id, city, department_name FROM employees e JOIN departments d ON d.department_id = e.department_id JOIN locations l ON d.location_id = l.location_id; … Copyright © 2004, Oracle. All rights reserved.

Retrieving Records with Non-Equijoins SELECT e.last_name, e.salary, j.grade_level FROM employees e JOIN job_grades j ON e.salary BETWEEN j.lowest_sal AND j.highest_sal; … Copyright © 2004, Oracle. All rights reserved.

INNER Versus OUTER Joins • In SQL:1999, the join of two tables returning only matched rows is called an inner join. • A join between two tables that returns the results of the inner join as well as the unmatched rows from the left (or right) tables is called a left (or right) outer join. • A join between two tables that returns the results of an inner join as well as the results of a left and right join is a full outer join. Copyright © 2004, Oracle. All rights reserved.

LEFT OUTER JOIN SELECT e.last_name, e.department_id, d.department_name FROM employees e LEFT OUTER JOIN departments d ON (e.department_id = d.department_id) ; … Copyright © 2004, Oracle. All rights reserved.

RIGHT OUTER JOIN SELECT e.last_name, e.department_id, d.department_name FROM employees e RIGHT OUTER JOIN departments d ON (e.department_id = d.department_id) ; … Copyright © 2004, Oracle. All rights reserved.

FULL OUTER JOIN SELECT e.last_name, d.department_id, d.department_name FROM employees e FULL OUTER JOIN departments d ON (e.department_id = d.department_id) ; … Copyright © 2004, Oracle. All rights reserved.

Cartesian Products • A Cartesian product is formed when: – A join condition is omitted – A join condition is invalid – All rows in the first table are joined to all rows in the second table • To avoid a Cartesian product, always include a valid join condition. Copyright © 2004, Oracle. All rights reserved.

Creating Cross Joins • The CROSS JOIN clause produces the cross- product of two tables. • This is also called a Cartesian product between the two tables. SELECT last_name, department_name FROM employees CROSS JOIN departments ; … Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to use joins to display data from multiple tables by using: • Equijoins • Non-equijoins • Outer joins • Self-joins • Cross joins • Natural joins • Full (or two-sided) outer joins Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Define subqueries • Describe the types of problems that subqueries can solve • List the types of subqueries • Write single-row and multiple-row subqueries Copyright © 2004, Oracle. All rights reserved.

Using a Subquery to Solve a Problem Who has a salary greater than Abel’s? Main query: Which employees have salaries greater than Abel’s salary? Subquery: What is Abel’s salary? Copyright © 2004, Oracle. All rights reserved.

Subquery Syntax SELECT select_list FROM table WHERE expr operator (SELECT select_list FROM table); • The subquery (inner query) executes once before the main query (outer query). • The result of the subquery is used by the main query. Copyright © 2004, Oracle. All rights reserved.

Guidelines for Using Subqueries • Enclose subqueries in parentheses. • Place subqueries on the right side of the comparison condition. • The ORDER BY clause in the subquery is not needed unless you are performing Top-N analysis. • Use single-row operators with single-row subqueries, and use multiple-row operators with multiple-row subqueries. Copyright © 2004, Oracle. All rights reserved.

Single-Row Subqueries • Return only one row • Use single-row comparison operators Operator Meaning = Equal to > Greater than >= Greater than or equal to < Less than <= Less than or equal to <> Not equal to Copyright © 2004, Oracle. All rights reserved.

Executing Single-Row Subqueries SELECT last_name, job_id, salary FROM employees WHERE job_id = ST_CLERK (SELECT job_id FROM employees WHERE employee_id = 141) AND salary > 2600 (SELECT salary FROM employees WHERE employee_id = 143); Copyright © 2004, Oracle. All rights reserved.

The HAVING Clause with Subqueries • The Oracle server executes subqueries first. • The Oracle server returns results into the HAVING clause of the main query. SELECT department_id, MIN(salary) FROM employees GROUP BY department_id 2500 HAVING MIN(salary) > (SELECT MIN(salary) FROM employees WHERE department_id = 50); Copyright © 2004, Oracle. All rights reserved.

What Is Wrong with This Statement? SELECT employee_id, last_name FROM employees WHERE salary = (SELECT MIN(salary) FROM employees GROUP BY department_id); ERROR at line 4: ORA-01427: single-row subquery returns more than one row Single-row operator with multiple-row subquery Copyright © 2004, Oracle. All rights reserved.

Will This Statement Return Rows? SELECT last_name, job_id FROM employees WHERE job_id = (SELECT job_id FROM employees WHERE last_name = 'Haas'); no rows selected Subquery returns no values. Copyright © 2004, Oracle. All rights reserved.

Multiple-Row Subqueries • Return more than one row • Use multiple-row comparison operators Operator Meaning IN Equal to any member in the list ANY Compare value to each value returned by the subquery ALL Compare value to every value returned by the subquery Copyright © 2004, Oracle. All rights reserved.

Using the ANY Operator in Multiple-Row Subqueries SELECT employee_id, last_name, job_id, salary FROM employees 9000, 6000, 4200 WHERE salary < ANY (SELECT salary FROM employees WHERE job_id = 'IT_PROG') AND job_id <> 'IT_PROG'; … Copyright © 2004, Oracle. All rights reserved.

Using the ALL Operator in Multiple-Row Subqueries SELECT employee_id, last_name, job_id, salary FROM employees 9000, 6000, 4200 WHERE salary < ALL (SELECT salary FROM employees WHERE job_id = 'IT_PROG') AND job_id <> 'IT_PROG'; Copyright © 2004, Oracle. All rights reserved.

Null Values in a Subquery SELECT emp.last_name FROM employees emp WHERE emp.employee_id NOT IN (SELECT mgr.manager_id FROM employees mgr); no rows selected Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Identify when a subquery can help solve a question • Write subqueries when a query is based on unknown values SELECT select_list FROM table WHERE expr operator (SELECT select_list FROM table); Copyright © 2004, Oracle. All rights reserved.

Practice 6: Overview This practice covers the following topics: • Creating subqueries to query values based on unknown criteria • Using subqueries to find out which values exist in one set of data and not in another Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Describe set operators • Use a set operator to combine multiple queries into a single query • Control the order of rows returned Copyright © 2004, Oracle. All rights reserved.

Tables Used in This Lesson The tables used in this lesson are: • EMPLOYEES: Provides details regarding all current employees • JOB_HISTORY: Records the details of the start date and end date of the former job, and the job identification number and department when an employee switches jobs Copyright © 2004, Oracle. All rights reserved.

Using the UNION Operator Display the current and previous job details of all employees. Display each employee only once. SELECT employee_id, job_id FROM employees UNION SELECT employee_id, job_id FROM job_history; … … Copyright © 2004, Oracle. All rights reserved.

Using the UNION ALL Operator Display the current and previous departments of all employees. SELECT employee_id, job_id, department_id FROM employees UNION ALL SELECT employee_id, job_id, department_id FROM job_history ORDER BY employee_id; … … Copyright © 2004, Oracle. All rights reserved.

Using the INTERSECT Operator Display the employee IDs and job IDs of those employees who currently have a job title that is the same as their job title when they were initially hired (that is, they changed jobs but have now gone back to doing their original job). SELECT employee_id, job_id FROM employees INTERSECT SELECT employee_id, job_id FROM job_history; Copyright © 2004, Oracle. All rights reserved.

MINUS Operator Display the employee IDs of those employees who have not changed their jobs even once. SELECT employee_id,job_id FROM employees MINUS SELECT employee_id,job_id FROM job_history; … Copyright © 2004, Oracle. All rights reserved.

Set Operator Guidelines • The expressions in the SELECT lists must match in number and data type. • Parentheses can be used to alter the sequence of execution. • The ORDER BY clause: – Can appear only at the very end of the statement – Will accept the column name, aliases from the first SELECT statement, or the positional notation Copyright © 2004, Oracle. All rights reserved.

The Oracle Server and Set Operators • Duplicate rows are automatically eliminated except in UNION ALL. • Column names from the first query appear in the result. • The output is sorted in ascending order by default except in UNION ALL. Copyright © 2004, Oracle. All rights reserved.

Matching the SELECT Statements Using the UNION operator, display the department ID, location, and hire date for all employees. SELECT department_id, TO_NUMBER(null) location, hire_date FROM employees UNION SELECT department_id, location_id, TO_DATE(null) FROM departments; … Copyright © 2004, Oracle. All rights reserved.

Matching the SELECT Statement: Example Using the UNION operator, display the employee ID, job ID, and salary of all employees. SELECT employee_id, job_id,salary FROM employees UNION SELECT employee_id, job_id,0 FROM job_history; … Copyright © 2004, Oracle. All rights reserved.

Controlling the Order of Rows Produce an English sentence using two UNION operators. COLUMN a_dummy NOPRINT SELECT 'sing' AS "My dream", 3 a_dummy FROM dual UNION SELECT 'I''d like to teach', 1 a_dummy FROM dual UNION SELECT 'the world to', 2 a_dummy FROM dual ORDER BY a_dummy; Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Use UNION to return all distinct rows • Use UNION ALL to return all rows, including duplicates • Use INTERSECT to return all rows that are shared by both queries • Use MINUS to return all distinct rows that are selected by the first query but not by the second • Use ORDER BY only at the very end of the statement Copyright © 2004, Oracle. All rights reserved.

Practice 7: Overview In this practice, you use the set operators to create reports: • Using the UNION operator • Using the INTERSECTION operator • Using the MINUS operator Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Describe each data manipulation language (DML) statement • Insert rows into a table • Update rows in a table • Delete rows from a table • Control transactions Copyright © 2004, Oracle. All rights reserved.

Data Manipulation Language • A DML statement is executed when you: – Add new rows to a table – Modify existing rows in a table – Remove existing rows from a table • A transaction consists of a collection of DML statements that form a logical unit of work. Copyright © 2004, Oracle. All rights reserved.

INSERT Statement Syntax • Add new rows to a table by using the INSERT statement: INSERT INTO table [(column [, column...])] VALUES (value [, value...]); • With this syntax, only one row is inserted at a time. Copyright © 2004, Oracle. All rights reserved.

Inserting New Rows • Insert a new row containing values for each column. • List values in the default order of the columns in the table. • Optionally, list the columns in the INSERT clause. INSERT INTO departments(department_id, department_name, manager_id, location_id) VALUES (70, 'Public Relations', 100, 1700); 1 row created. • Enclose character and date values in single quotation marks. Copyright © 2004, Oracle. All rights reserved.

Inserting Rows with Null Values • Implicit method: Omit the column from the column list. INSERT INTO departments (department_id, department_name ) VALUES (30, 'Purchasing'); 1 row created. • Explicit method: Specify the NULL keyword in the VALUES clause. INSERT INTO departments VALUES (100, 'Finance', NULL, NULL); 1 row created. Copyright © 2004, Oracle. All rights reserved.

Inserting Special Values The SYSDATE function records the current date and time. INSERT INTO employees (employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, commission_pct, manager_id, department_id) VALUES (113, 'Louis', 'Popp', 'LPOPP', '515.124.4567', SYSDATE, 'AC_ACCOUNT', 6900, NULL, 205, 100); 1 row created. Copyright © 2004, Oracle. All rights reserved.

Inserting Specific Date Values • Add a new employee. INSERT INTO employees VALUES (114, 'Den', 'Raphealy', 'DRAPHEAL', '515.127.4561', TO_DATE('FEB 3, 1999', 'MON DD, YYYY'), 'AC_ACCOUNT', 11000, NULL, 100, 30); 1 row created. • Verify your addition. Copyright © 2004, Oracle. All rights reserved.

Creating a Script • Use & substitution in a SQL statement to prompt for values. • & is a placeholder for the variable value. INSERT INTO departments (department_id, department_name, location_id) VALUES (&department_id, '&department_name',&location); 1 row created. Copyright © 2004, Oracle. All rights reserved.

Copying Rows from Another Table • Write your INSERT statement with a subquery: INSERT INTO sales_reps(id, name, salary, commission_pct) SELECT employee_id, last_name, salary, commission_pct FROM employees WHERE job_id LIKE '%REP%'; 4 rows created. • Do not use the VALUES clause. • Match the number of columns in the INSERT clause to those in the subquery. Copyright © 2004, Oracle. All rights reserved.

UPDATE Statement Syntax • Modify existing rows with the UPDATE statement: UPDATE table SET column = value [, column = value, ...] [WHERE condition]; • Update more than one row at a time (if required). Copyright © 2004, Oracle. All rights reserved.

Updating Rows in a Table • Specific row or rows are modified if you specify the WHERE clause: UPDATE employees SET department_id = 70 WHERE employee_id = 113; 1 row updated. • All rows in the table are modified if you omit the WHERE clause: UPDATE copy_emp SET department_id = 110; 22 rows updated. Copyright © 2004, Oracle. All rights reserved.

Updating Two Columns with a Subquery Update employee 114’s job and salary to match that of employee 205. UPDATE employees SET job_id = (SELECT job_id FROM employees WHERE employee_id = 205), salary = (SELECT salary FROM employees WHERE employee_id = 205) WHERE employee_id = 114; 1 row updated. Copyright © 2004, Oracle. All rights reserved.

Updating Rows Based on Another Table Use subqueries in UPDATE statements to update rows in a table based on values from another table: UPDATE copy_emp SET department_id = (SELECT department_id FROM employees WHERE employee_id = 100) WHERE job_id = (SELECT job_id FROM employees WHERE employee_id = 200); 1 row updated. Copyright © 2004, Oracle. All rights reserved.

Deleting Rows from a Table • Specific rows are deleted if you specify the WHERE clause: DELETE FROM departments WHERE department_name = 'Finance'; 1 row deleted. • All rows in the table are deleted if you omit the WHERE clause: DELETE FROM copy_emp; 22 rows deleted. Copyright © 2004, Oracle. All rights reserved.

Deleting Rows Based on Another Table Use subqueries in DELETE statements to remove rows from a table based on values from another table: DELETE FROM employees WHERE department_id = (SELECT department_id FROM departments WHERE department_name LIKE '%Public%'); 1 row deleted. Copyright © 2004, Oracle. All rights reserved.

TRUNCATE Statement • Removes all rows from a table, leaving the table empty and the table structure intact • Is a data definition language (DDL) statement rather than a DML statement; cannot easily be undone • Syntax: TRUNCATE TABLE table_name; • Example: TRUNCATE TABLE copy_emp; Copyright © 2004, Oracle. All rights reserved.

Using a Subquery in an INSERT Statement INSERT INTO (SELECT employee_id, last_name, email, hire_date, job_id, salary, department_id FROM employees WHERE department_id = 50) VALUES (99999, 'Taylor', 'DTAYLOR', TO_DATE('07-JUN-99', 'DD-MON-RR'), 'ST_CLERK', 5000, 50); 1 row created. Copyright © 2004, Oracle. All rights reserved.

Using a Subquery in an INSERT Statement Verify the results: SELECT employee_id, last_name, email, hire_date, job_id, salary, department_id FROM employees WHERE department_id = 50; Copyright © 2004, Oracle. All rights reserved.

Database Transactions A database transaction consists of one of the following: • DML statements that constitute one consistent change to the data • One DDL statement • One data control language (DCL) statement Copyright © 2004, Oracle. All rights reserved.

Database Transactions • Begin when the first DML SQL statement is executed. • End with one of the following events: – A COMMIT or ROLLBACK statement is issued. – A DDL or DCL statement executes (automatic commit). – The user exits iSQL*Plus. – The system crashes. Copyright © 2004, Oracle. All rights reserved.

Advantages of COMMIT and ROLLBACK Statements With COMMIT and ROLLBACK statements, you can: • Ensure data consistency • Preview data changes before making changes permanent • Group logically related operations Copyright © 2004, Oracle. All rights reserved.

Controlling Transactions Time COMMIT Transaction DELETE SAVEPOINT A INSERT UPDATE SAVEPOINT B INSERT ROLLBACK ROLLBACK ROLLBACK to SAVEPOINT B to SAVEPOINT A Copyright © 2004, Oracle. All rights reserved.

Rolling Back Changes to a Marker • Create a marker in a current transaction by using the SAVEPOINT statement. • Roll back to that marker by using the ROLLBACK TO SAVEPOINT statement. UPDATE... SAVEPOINT update_done; Savepoint created. INSERT... ROLLBACK TO update_done; Rollback complete. Copyright © 2004, Oracle. All rights reserved.

Implicit Transaction Processing • An automatic commit occurs under the following circumstances: – DDL statement is issued – DCL statement is issued – Normal exit from iSQL*Plus, without explicitly issuing COMMIT or ROLLBACK statements • An automatic rollback occurs under an abnormal termination of iSQL*Plus or a system failure. Copyright © 2004, Oracle. All rights reserved.

State of the Data Before COMMIT or ROLLBACK • The previous state of the data can be recovered. • The current user can review the results of the DML operations by using the SELECT statement. • Other users cannot view the results of the DML statements by the current user. • The affected rows are locked; other users cannot change the data in the affected rows. Copyright © 2004, Oracle. All rights reserved.

State of the Data After COMMIT • Data changes are made permanent in the database. • The previous state of the data is permanently lost. • All users can view the results. • Locks on the affected rows are released; those rows are available for other users to manipulate. • All savepoints are erased. Copyright © 2004, Oracle. All rights reserved.

Committing Data • Make the changes: DELETE FROM employees WHERE employee_id = 99999; 1 row deleted. INSERT INTO departments VALUES (290, 'Corporate Tax', NULL, 1700); 1 row created. • Commit the changes: COMMIT; Commit complete. Copyright © 2004, Oracle. All rights reserved.

State of the Data After ROLLBACK Discard all pending changes by using the ROLLBACK statement: • Data changes are undone. • Previous state of the data is restored. • Locks on the affected rows are released. DELETE FROM copy_emp; 22 rows deleted. ROLLBACK ; Rollback complete. Copyright © 2004, Oracle. All rights reserved.

State of the Data After ROLLBACK DELETE FROM test; 25,000 rows deleted. ROLLBACK; Rollback complete. DELETE FROM test WHERE id = 100; 1 row deleted. SELECT * FROM test WHERE id = 100; No rows selected. COMMIT; Commit complete. Copyright © 2004, Oracle. All rights reserved.

Statement-Level Rollback • If a single DML statement fails during execution, only that statement is rolled back. • The Oracle server implements an implicit savepoint. • All other changes are retained. • The user should terminate transactions explicitly by executing a COMMIT or ROLLBACK statement. Copyright © 2004, Oracle. All rights reserved.

Read Consistency • Read consistency guarantees a consistent view of the data at all times. • Changes made by one user do not conflict with changes made by another user. • Read consistency ensures that on the same data: – Readers do not wait for writers – Writers do not wait for readers Copyright © 2004, Oracle. All rights reserved.

Implementation of Read Consistency User A UPDATE employees Data SET salary = 7000 blocks WHERE last_name = 'Grant'; Undo segments Changed SELECT * and FROM userA.employees; Read- unchanged consistent data image Before change (“old” data) User B Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to use the following statements: Function Description INSERT Adds a new row to the table UPDATE Modifies existing rows in the table DELETE Removes existing rows from the table COMMIT Makes all pending changes permanent SAVEPOINT Is used to roll back to the savepoint marker ROLLBACK Discards all pending data changes Copyright © 2004, Oracle. All rights reserved.

Practice 8: Overview This practice covers the following topics: • Inserting rows into the tables • Updating and deleting rows in the table • Controlling transactions Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Categorize the main database objects • Review the table structure • List the data types that are available for columns • Create a simple table • Understand how constraints are created at the time of table creation • Describe how schema objects work Copyright © 2004, Oracle. All rights reserved.

Database Objects Object Description Table Basic unit of storage; composed of rows View Logically represents subsets of data from one or more tables Sequence Generates numeric values Index Improves the performance of some queries Synonym Gives alternative names to objects Copyright © 2004, Oracle. All rights reserved.

Naming Rules Table names and column names: • Must begin with a letter • Must be 1–30 characters long • Must contain only A–Z, a–z, 0–9, _, $, and # • Must not duplicate the name of another object owned by the same user • Must not be an Oracle server reserved word Copyright © 2004, Oracle. All rights reserved.

CREATE TABLE Statement • You must have: – CREATE TABLE privilege – A storage area CREATE TABLE [schema.]table (column datatype [DEFAULT expr][, ...]); • You specify: – Table name – Column name, column data type, and column size Copyright © 2004, Oracle. All rights reserved.

Referencing Another User’s Tables • Tables belonging to other users are not in the user’s schema. • You should use the owner’s name as a prefix to those tables. USERA USERB SELECT * SELECT * FROM userB.employees; FROM userA.employees; Copyright © 2004, Oracle. All rights reserved.

DEFAULT Option • Specify a default value for a column during an insert. ... hire_date DATE DEFAULT SYSDATE, ... • Literal values, expressions, or SQL functions are legal values. • Another column’s name or a pseudocolumn are illegal values. • The default data type must match the column data type. CREATE TABLE hire_dates (id NUMBER(8), hire_date DATE DEFAULT SYSDATE); Table created. Copyright © 2004, Oracle. All rights reserved.

Creating Tables • Create the table. CREATE TABLE dept (deptno NUMBER(2), dname VARCHAR2(14), loc VARCHAR2(13), create_date DATE DEFAULT SYSDATE); Table created. • Confirm table creation. DESCRIBE dept Copyright © 2004, Oracle. All rights reserved.

Data Types Data Type Description VARCHAR2(size) Variable-length character data CHAR(size) Fixed-length character data NUMBER(p,s) Variable-length numeric data DATE Date and time values LONG Variable-length character data (up to 2 GB) CLOB Character data (up to 4 GB) RAW and LONG Raw binary data RAW BLOB Binary data (up to 4 GB) BFILE Binary data stored in an external file (up to 4 GB) ROWID A base-64 number system representing the unique address of a row in its table Copyright © 2004, Oracle. All rights reserved.

Datetime Data Types You can use several datetime data types: Data Type Description TIMESTAMP Date with fractional seconds INTERVAL YEAR TO Stored as an interval of years MONTH and months INTERVAL DAY TO Stored as an interval of days, hours, SECOND minutes, and seconds Copyright © 2004, Oracle. All rights reserved.

Datetime Data Types • The TIMESTAMP data type is an extension of the DATE data type. • It stores the year, month, and day of the DATE data type plus hour, minute, and second values as well as the fractional second value. • You can optionally specify the time zone. TIMESTAMP[(fractional_seconds_precision)] TIMESTAMP[(fractional_seconds_precision)] WITH TIME ZONE TIMESTAMP[(fractional_seconds_precision)] WITH LOCAL TIME ZONE Copyright © 2004, Oracle. All rights reserved.

Datetime Data Types • The INTERVAL YEAR TO MONTH data type stores a period of time using the YEAR and MONTH datetime fields: INTERVAL YEAR [(year_precision)] TO MONTH • The INTERVAL DAY TO SECOND data type stores a period of time in terms of days, hours, minutes, and seconds: INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)] Copyright © 2004, Oracle. All rights reserved.

Including Constraints • Constraints enforce rules at the table level. • Constraints prevent the deletion of a table if there are dependencies. • The following constraint types are valid: – NOT NULL – UNIQUE – PRIMARY KEY – FOREIGN KEY – CHECK Copyright © 2004, Oracle. All rights reserved.

Constraint Guidelines • You can name a constraint, or the Oracle server generates a name by using the SYS_Cn format. • Create a constraint at either of the following times: – At the same time as the table is created – After the table has been created • Define a constraint at the column or table level. • View a constraint in the data dictionary. Copyright © 2004, Oracle. All rights reserved.

Defining Constraints • Syntax: CREATE TABLE [schema.]table (column datatype [DEFAULT expr] [column_constraint], ... [table_constraint][,...]); • Column-level constraint: column [CONSTRAINT constraint_name] constraint_type, • Table-level constraint: column,... [CONSTRAINT constraint_name] constraint_type (column, ...), Copyright © 2004, Oracle. All rights reserved.

Defining Constraints • Column-level constraint: CREATE TABLE employees( employee_id NUMBER(6) CONSTRAINT emp_emp_id_pk PRIMARY KEY, 1 first_name VARCHAR2(20), ...); • Table-level constraint: CREATE TABLE employees( employee_id NUMBER(6), first_name VARCHAR2(20), ... job_id VARCHAR2(10) NOT NULL, 2 CONSTRAINT emp_emp_id_pk PRIMARY KEY (EMPLOYEE_ID)); Copyright © 2004, Oracle. All rights reserved.

NOT NULL Constraint Ensures that null values are not permitted for the column: … NOT NULL constraint NOT NULL Absence of NOT NULL (No row can contain constraint constraint a null value for (Any row can contain this column.) a null value for this column.) Copyright © 2004, Oracle. All rights reserved.

UNIQUE Constraint Defined at either the table level or the column level: CREATE TABLE employees( employee_id NUMBER(6), last_name VARCHAR2(25) NOT NULL, email VARCHAR2(25), salary NUMBER(8,2), commission_pct NUMBER(2,2), hire_date DATE NOT NULL, ... CONSTRAINT emp_email_uk UNIQUE(email)); Copyright © 2004, Oracle. All rights reserved.

FOREIGN KEY Constraint Defined at either the table level or the column level: CREATE TABLE employees( employee_id NUMBER(6), last_name VARCHAR2(25) NOT NULL, email VARCHAR2(25), salary NUMBER(8,2), commission_pct NUMBER(2,2), hire_date DATE NOT NULL, ... department_id NUMBER(4), CONSTRAINT emp_dept_fk FOREIGN KEY (department_id) REFERENCES departments(department_id), CONSTRAINT emp_email_uk UNIQUE(email)); Copyright © 2004, Oracle. All rights reserved.

FOREIGN KEY Constraint: Keywords • FOREIGN KEY: Defines the column in the child table at the table-constraint level • REFERENCES: Identifies the table and column in the parent table • ON DELETE CASCADE: Deletes the dependent rows in the child table when a row in the parent table is deleted • ON DELETE SET NULL: Converts dependent foreign key values to null Copyright © 2004, Oracle. All rights reserved.

CHECK Constraint • Defines a condition that each row must satisfy • The following expressions are not allowed: – References to CURRVAL, NEXTVAL, LEVEL, and ROWNUM pseudocolumns – Calls to SYSDATE, UID, USER, and USERENV functions – Queries that refer to other values in other rows ..., salary NUMBER(2) CONSTRAINT emp_salary_min CHECK (salary > 0),... Copyright © 2004, Oracle. All rights reserved.

CREATE TABLE: Example CREATE TABLE employees ( employee_id NUMBER(6) CONSTRAINT emp_employee_id PRIMARY KEY , first_name VARCHAR2(20) , last_name VARCHAR2(25) CONSTRAINT emp_last_name_nn NOT NULL , email VARCHAR2(25) CONSTRAINT emp_email_nn NOT NULL CONSTRAINT emp_email_uk UNIQUE , phone_number VARCHAR2(20) , hire_date DATE CONSTRAINT emp_hire_date_nn NOT NULL , job_id VARCHAR2(10) CONSTRAINT emp_job_nn NOT NULL , salary NUMBER(8,2) CONSTRAINT emp_salary_ck CHECK (salary>0) , commission_pct NUMBER(2,2) , manager_id NUMBER(6) , department_id NUMBER(4) CONSTRAINT emp_dept_fk REFERENCES departments (department_id)); Copyright © 2004, Oracle. All rights reserved.

Violating Constraints UPDATE employees SET department_id = 55 WHERE department_id = 110; UPDATE employees * ERROR at line 1: ORA-02291: integrity constraint (HR.EMP_DEPT_FK) violated - parent key not found Department 55 does not exist. Copyright © 2004, Oracle. All rights reserved.

Violating Constraints You cannot delete a row that contains a primary key that is used as a foreign key in another table. DELETE FROM departments WHERE department_id = 60; DELETE FROM departments * ERROR at line 1: ORA-02292: integrity constraint (HR.EMP_DEPT_FK) violated - child record found Copyright © 2004, Oracle. All rights reserved.

Creating a Table by Using a Subquery • Create a table and insert rows by combining the CREATE TABLE statement and the AS subquery option. CREATE TABLE table [(column, column...)] AS subquery; • Match the number of specified columns to the number of subquery columns. • Define columns with column names and default values. Copyright © 2004, Oracle. All rights reserved.

Creating a Table by Using a Subquery CREATE TABLE dept80 AS SELECT employee_id, last_name, salary*12 ANNSAL, hire_date FROM employees WHERE department_id = 80; Table created. DESCRIBE dept80 Copyright © 2004, Oracle. All rights reserved.

ALTER TABLE Statement Use the ALTER TABLE statement to: • Add a new column • Modify an existing column • Define a default value for the new column • Drop a column Copyright © 2004, Oracle. All rights reserved.

Dropping a Table • All data and structure in the table are deleted. • Any pending transactions are committed. • All indexes are dropped. • All constraints are dropped. • You cannot roll back the DROP TABLE statement. DROP TABLE dept80; Table dropped. Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to use the CREATE TABLE statement to create a table and include constraints. • Categorize the main database objects • Review the table structure • List the data types that are available for columns • Create a simple table • Understand how constraints are created at the time of table creation • Describe how schema objects work Copyright © 2004, Oracle. All rights reserved.

Practice 9: Overview This practice covers the following topics: • Creating new tables • Creating a new table by using the CREATE TABLE AS syntax • Verifying that tables exist • Dropping tables Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Create simple and complex views • Retrieve data from views • Create, maintain, and use sequences • Create and maintain indexes • Create private and public synonyms Copyright © 2004, Oracle. All rights reserved.

Simple Views and Complex Views Feature Simple Views Complex Views Number of tables One One or more Contain functions No Yes Contain groups of data No Yes DML operations Yes Not always through a view Copyright © 2004, Oracle. All rights reserved.

Creating a View • You embed a subquery in the CREATE VIEW statement: CREATE [OR REPLACE] [FORCE|NOFORCE] VIEW view [(alias[, alias]...)] AS subquery [WITH CHECK OPTION [CONSTRAINT constraint]] [WITH READ ONLY [CONSTRAINT constraint]]; • The subquery can contain complex SELECT syntax. Copyright © 2004, Oracle. All rights reserved.

Creating a View • Create the EMPVU80 view, which contains details of employees in department 80: CREATE VIEW empvu80 AS SELECT employee_id, last_name, salary FROM employees WHERE department_id = 80; View created. • Describe the structure of the view by using the iSQL*Plus DESCRIBE command: DESCRIBE empvu80 Copyright © 2004, Oracle. All rights reserved.

Creating a View • Create a view by using column aliases in the subquery: CREATE VIEW salvu50 AS SELECT employee_id ID_NUMBER, last_name NAME, salary*12 ANN_SALARY FROM employees WHERE department_id = 50; View created. • Select the columns from this view by the given alias names: Copyright © 2004, Oracle. All rights reserved.

Modifying a View • Modify the EMPVU80 view by using a CREATE OR REPLACE VIEW clause. Add an alias for each column name: CREATE OR REPLACE VIEW empvu80 (id_number, name, sal, department_id) AS SELECT employee_id, first_name || ' ' || last_name, salary, department_id FROM employees WHERE department_id = 80; View created. • Column aliases in the CREATE OR REPLACE VIEW clause are listed in the same order as the columns in the subquery. Copyright © 2004, Oracle. All rights reserved.

Creating a Complex View Create a complex view that contains group functions to display values from two tables: CREATE OR REPLACE VIEW dept_sum_vu (name, minsal, maxsal, avgsal) AS SELECT d.department_name, MIN(e.salary), MAX(e.salary),AVG(e.salary) FROM employees e JOIN departments d ON (e.department_id = d.department_id) GROUP BY d.department_name; View created. Copyright © 2004, Oracle. All rights reserved.

Rules for Performing DML Operations on a View • You can usually perform DML operations on simple views. • You cannot remove a row if the view contains the following: – Group functions – A GROUP BY clause – The DISTINCT keyword – The pseudocolumn ROWNUM keyword Copyright © 2004, Oracle. All rights reserved.

Rules for Performing DML Operations on a View You cannot modify data in a view if it contains: • Group functions • A GROUP BY clause • The DISTINCT keyword • The pseudocolumn ROWNUM keyword • Columns defined by expressions Copyright © 2004, Oracle. All rights reserved.

Rules for Performing DML Operations on a View You cannot add data through a view if the view includes: • Group functions • A GROUP BY clause • The DISTINCT keyword • The pseudocolumn ROWNUM keyword • Columns defined by expressions • NOT NULL columns in the base tables that are not selected by the view Copyright © 2004, Oracle. All rights reserved.

Using the WITH CHECK OPTION Clause • You can ensure that DML operations performed on the view stay in the domain of the view by using the WITH CHECK OPTION clause: CREATE OR REPLACE VIEW empvu20 AS SELECT * FROM employees WHERE department_id = 20 WITH CHECK OPTION CONSTRAINT empvu20_ck ; View created. • Any attempt to change the department number for any row in the view fails because it violates the WITH CHECK OPTION constraint. Copyright © 2004, Oracle. All rights reserved.

Denying DML Operations • You can ensure that no DML operations occur by adding the WITH READ ONLY option to your view definition. • Any attempt to perform a DML operation on any row in the view results in an Oracle server error. Copyright © 2004, Oracle. All rights reserved.

Denying DML Operations CREATE OR REPLACE VIEW empvu10 (employee_number, employee_name, job_title) AS SELECT employee_id, last_name, job_id FROM employees WHERE department_id = 10 WITH READ ONLY ; View created. Copyright © 2004, Oracle. All rights reserved.

Removing a View You can remove a view without losing data because a view is based on underlying tables in the database. DROP VIEW view; DROP VIEW empvu80; View dropped. Copyright © 2004, Oracle. All rights reserved.

Practice 10: Overview of Part 1 This practice covers the following topics: • Creating a simple view • Creating a complex view • Creating a view with a check constraint • Attempting to modify data in the view • Removing views Copyright © 2004, Oracle. All rights reserved.

Sequences Object Description Table Basic unit of storage; composed of rows View Logically represents subsets of data from one or more tables Sequence Generates numeric values Index Improves the performance of some queries Synonym Gives alternative names to objects Copyright © 2004, Oracle. All rights reserved.

Sequences A sequence: • Can automatically generate unique numbers • Is a sharable object • Can be used to create a primary key value • Replaces application code • Speeds up the efficiency of accessing sequence values when cached in memory 2 4 6 8 10 1 3 5 7 9 Copyright © 2004, Oracle. All rights reserved.

CREATE SEQUENCE Statement: Syntax Define a sequence to generate sequential numbers automatically: CREATE SEQUENCE sequence [INCREMENT BY n] [START WITH n] [{MAXVALUE n | NOMAXVALUE}] [{MINVALUE n | NOMINVALUE}] [{CYCLE | NOCYCLE}] [{CACHE n | NOCACHE}]; Copyright © 2004, Oracle. All rights reserved.

Creating a Sequence • Create a sequence named DEPT_DEPTID_SEQ to be used for the primary key of the DEPARTMENTS table. • Do not use the CYCLE option. CREATE SEQUENCE dept_deptid_seq INCREMENT BY 10 START WITH 120 MAXVALUE 9999 NOCACHE NOCYCLE; Sequence created. Copyright © 2004, Oracle. All rights reserved.

NEXTVAL and CURRVAL Pseudocolumns • NEXTVAL returns the next available sequence value. It returns a unique value every time it is referenced, even for different users. • CURRVAL obtains the current sequence value. • NEXTVAL must be issued for that sequence before CURRVAL contains a value. Copyright © 2004, Oracle. All rights reserved.

Using a Sequence • Insert a new department named “Support” in location ID 2500: INSERT INTO departments(department_id, department_name, location_id) VALUES (dept_deptid_seq.NEXTVAL, 'Support', 2500); 1 row created. • View the current value for the DEPT_DEPTID_SEQ sequence: SELECT dept_deptid_seq.CURRVAL FROM dual; Copyright © 2004, Oracle. All rights reserved.

Caching Sequence Values • Caching sequence values in memory gives faster access to those values. • Gaps in sequence values can occur when: – A rollback occurs – The system crashes – A sequence is used in another table Copyright © 2004, Oracle. All rights reserved.

Modifying a Sequence Change the increment value, maximum value, minimum value, cycle option, or cache option: ALTER SEQUENCE dept_deptid_seq INCREMENT BY 20 MAXVALUE 999999 NOCACHE NOCYCLE; Sequence altered. Copyright © 2004, Oracle. All rights reserved.

Guidelines for Modifying a Sequence • You must be the owner or have the ALTER privilege for the sequence. • Only future sequence numbers are affected. • The sequence must be dropped and re-created to restart the sequence at a different number. • Some validation is performed. • To remove a sequence, use the DROP statement: DROP SEQUENCE dept_deptid_seq; Sequence dropped. Copyright © 2004, Oracle. All rights reserved.

Indexes Object Description Table Basic unit of storage; composed of rows View Logically represents subsets of data from one or more tables Sequence Generates numeric values Index Improves the performance of some queries Synonym Gives alternative names to objects Copyright © 2004, Oracle. All rights reserved.

Indexes An index: • Is a schema object • Can be used by the Oracle server to speed up the retrieval of rows by using a pointer • Can reduce disk I/O by using a rapid path access method to locate data quickly • Is independent of the table that it indexes • Is used and maintained automatically by the Oracle server Copyright © 2004, Oracle. All rights reserved.

How Are Indexes Created? • Automatically: A unique index is created automatically when you define a PRIMARY KEY or UNIQUE constraint in a table definition. • Manually: Users can create nonunique indexes on columns to speed up access to the rows. Copyright © 2004, Oracle. All rights reserved.

Creating an Index • Create an index on one or more columns: CREATE INDEX index ON table (column[, column]...); • Improve the speed of query access to the LAST_NAME column in the EMPLOYEES table: CREATE INDEX emp_last_name_idx ON employees(last_name); Index created. Copyright © 2004, Oracle. All rights reserved.

Index Creation Guidelines Create an index when: A column contains a wide range of values A column contains a large number of null values One or more columns are frequently used together in a WHERE clause or a join condition The table is large and most queries are expected to retrieve less than 2% to 4% of the rows in the table Do not create an index when: The columns are not often used as a condition in the query The table is small or most queries are expected to retrieve more than 2% to 4% of the rows in the table The table is updated frequently The indexed columns are referenced as part of an expression Copyright © 2004, Oracle. All rights reserved.

Removing an Index • Remove an index from the data dictionary by using the DROP INDEX command: DROP INDEX index; • Remove the UPPER_LAST_NAME_IDX index from the data dictionary: DROP INDEX emp_last_name_idx; Index dropped. • To drop an index, you must be the owner of the index or have the DROP ANY INDEX privilege. Copyright © 2004, Oracle. All rights reserved.

Synonyms Object Description Table Basic unit of storage; composed of rows View Logically represents subsets of data from one or more tables Sequence Generates numeric values Index Improves the performance of some queries Synonym Gives alternative names to objects Copyright © 2004, Oracle. All rights reserved.

Synonyms Simplify access to objects by creating a synonym (another name for an object). With synonyms, you can: • Create an easier reference to a table that is owned by another user • Shorten lengthy object names CREATE [PUBLIC] SYNONYM synonym FOR object; Copyright © 2004, Oracle. All rights reserved.

Creating and Removing Synonyms • Create a shortened name for the DEPT_SUM_VU view: CREATE SYNONYM d_sum FOR dept_sum_vu; Synonym Created. • Drop a synonym: DROP SYNONYM d_sum; Synonym dropped. Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to: • Create, use, and remove views • Automatically generate sequence numbers by using a sequence generator • Create indexes to improve query retrieval speed • Use synonyms to provide alternative names for objects Copyright © 2004, Oracle. All rights reserved.

Practice 10: Overview of Part 2 This practice covers the following topics: • Creating sequences • Using sequences • Creating nonunique indexes • Creating synonyms Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Use the data dictionary views to research data on your objects • Query various data dictionary views Copyright © 2004, Oracle. All rights reserved.

The Data Dictionary Oracle server Tables containing Data dictionary business data: views: EMPLOYEES DICTIONARY DEPARTMENTS USER_OBJECTS LOCATIONS USER_TABLES JOB_HISTORY USER_TAB_COLUMNS ... ... Copyright © 2004, Oracle. All rights reserved.

Data Dictionary Structure View naming convention: View Prefix Purpose USER User’s view (what is in your schema; what you own) ALL Expanded user’s view (what you can access) DBA Database administrator’s view (what is in everyone’s schemas) V$ Performance-related data Copyright © 2004, Oracle. All rights reserved.

How to Use the Dictionary Views Start with DICTIONARY. It contains the names and descriptions of the dictionary tables and views. DESCRIBE DICTIONARY SELECT * FROM dictionary WHERE table_name = 'USER_OBJECTS'; Copyright © 2004, Oracle. All rights reserved.

USER_OBJECTS and ALL_OBJECTS Views USER_OBJECTS: • Query USER_OBJECTS to see all of the objects that are owned by you • Is a useful way to obtain a listing of all object names and types in your schema, plus the following information: – Date created – Date of last modification – Status (valid or invalid) ALL_OBJECTS: • Query ALL_OBJECTS to see all objects to which you have access Copyright © 2004, Oracle. All rights reserved.

Constraint Information • USER_CONSTRAINTS describes the constraint definitions on your tables. • USER_CONS_COLUMNS describes columns that are owned by you and that are specified in constraints. DESCRIBE user_constraints … Copyright © 2004, Oracle. All rights reserved.

Constraint Information SELECT constraint_name, constraint_type, search_condition, r_constraint_name, delete_rule, status FROM user_constraints WHERE table_name = 'EMPLOYEES'; Copyright © 2004, Oracle. All rights reserved.

Sequence Information • Verify your sequence values in the USER_SEQUENCES data dictionary table. SELECT sequence_name, min_value, max_value, increment_by, last_number FROM user_sequences; • The LAST_NUMBER column displays the next available sequence number if NOCACHE is specified. Copyright © 2004, Oracle. All rights reserved.

Adding Comments to a Table • You can add comments to a table or column by using the COMMENT statement: COMMENT ON TABLE employees IS 'Employee Information'; Comment created. • Comments can be viewed through the data dictionary views: – ALL_COL_COMMENTS – USER_COL_COMMENTS – ALL_TAB_COMMENTS – USER_TAB_COMMENTS Copyright © 2004, Oracle. All rights reserved.

Summary In this lesson, you should have learned how to find information about your objects through the following dictionary views: • DICTIONARY • USER_OBJECTS • USER_TABLES • USER_TAB_COLUMNS • USER_CONSTRAINTS • USER_CONS_COLUMNS • USER_VIEWS • USER_SEQUENCES • USER_TAB_SYNONYMS Copyright © 2004, Oracle. All rights reserved.

Practice 11: Overview This practice covers the following topics: • Querying the dictionary views for table and column information • Querying the dictionary views for constraint information • Querying the dictionary views for view information • Querying the dictionary views for sequence information • Querying the dictionary views for synonym information • Adding a comment to a table and querying the dictionary views for comment information Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this lesson, you should be able to do the following: • Write SELECT statements to access data from more than one table using equijoins and non- equijoins • Use outer joins to view data that generally does not meet a join condition • Join a table to itself by using a self-join Copyright © 2004, Oracle. All rights reserved.

Cartesian Products • A Cartesian product is formed when: – A join condition is omitted – A join condition is invalid – All rows in the first table are joined to all rows in the second table • To avoid a Cartesian product, always include a valid join condition in a WHERE clause. Copyright © 2004, Oracle. All rights reserved.

Types of Joins Oracle-proprietary joins SQL:1999–compliant joins (8i and earlier releases) • Equijoin • Cross join • Non-equijoin • Natural join • Outer join • Using clause • Self-join • Full (or two-sided) outer join • Arbitrary join condition for outer join Copyright © 2004, Oracle. All rights reserved.

Joining Tables Using Oracle Syntax Use a join to query data from more than one table: SELECT table1.column, table2.column FROM table1, table2 WHERE table1.column1 = table2.column2; • Write the join condition in the WHERE clause. • Prefix the column name with the table name when the same column name appears in more than one table. Copyright © 2004, Oracle. All rights reserved.

Retrieving Records with Equijoins SELECT employees.employee_id, employees.last_name, employees.department_id, departments.department_id, departments.location_id FROM employees, departments WHERE employees.department_id = departments.department_id; … Copyright © 2004, Oracle. All rights reserved.

Qualifying Ambiguous Column Names • Use table prefixes to qualify column names that are in multiple tables. • Use table prefixes to improve performance. • Use column aliases to distinguish columns that have identical names but reside in different tables. Copyright © 2004, Oracle. All rights reserved.

Using Table Aliases • Use table aliases to simplify queries. • Use table prefixes to improve performance. SELECT e.employee_id, e.last_name, e.department_id, d.department_id, d.location_id FROM employees e , departments d WHERE e.department_id = d.department_id; Copyright © 2004, Oracle. All rights reserved.

Joining More Than Two Tables EMPLOYEES DEPARTMENTS LOCATIONS … To join n tables together, you need a minimum of n–1 join conditions. For example, to join three tables, a minimum of two joins is required. Copyright © 2004, Oracle. All rights reserved.

Retrieving Records with Non-Equijoins SELECT e.last_name, e.salary, j.grade_level FROM employees e, job_grades j WHERE e.salary BETWEEN j.lowest_sal AND j.highest_sal; … Copyright © 2004, Oracle. All rights reserved.

Outer Joins Syntax • You use an outer join to see rows that do not meet the join condition. • The outer join operator is the plus sign (+). SELECT table1.column, table2.column FROM table1, table2 WHERE table1.column(+) = table2.column; SELECT table1.column, table2.column FROM table1, table2 WHERE table1.column = table2.column(+); Copyright © 2004, Oracle. All rights reserved.

Joining a Table to Itself SELECT worker.last_name || ' works for ' || manager.last_name FROM employees worker, employees manager WHERE worker.manager_id = manager.employee_id ; … Copyright © 2004, Oracle. All rights reserved.

Summary In this appendix, you should have learned how to use joins to display data from multiple tables by using Oracle-proprietary syntax for versions 8i and earlier. Copyright © 2004, Oracle. All rights reserved.

Objectives After completing this appendix, you should be able to do the following: • Log in to SQL*Plus • Edit SQL commands • Format output using SQL*Plus commands • Interact with script files Copyright © 2004, Oracle. All rights reserved.

SQL Statements Versus SQL*Plus Commands SQL SQL*Plus • A language • An environment • ANSI-standard • Oracle-proprietary • Keywords cannot be • Keywords can be abbreviated abbreviated • Statements manipulate • Commands do not data and table allow manipulation of definitions in the values in the database database SQL SQL SQL*Plus SQL*Plus statements buffer commands buffer Copyright © 2004, Oracle. All rights reserved.

Overview of SQL*Plus • Log in to SQL*Plus. • Describe the table structure. • Edit your SQL statement. • Execute SQL from SQL*Plus. • Save SQL statements to files and append SQL statements to files. • Execute saved files. • Load commands from file to buffer to edit. Copyright © 2004, Oracle. All rights reserved.

Displaying Table Structure SQL> DESCRIBE departments Name Null? Type ----------------------- -------- ------------ DEPARTMENT_ID NOT NULL NUMBER(4) DEPARTMENT_NAME NOT NULL VARCHAR2(30) MANAGER_ID NUMBER(6) LOCATION_ID NUMBER(4) Copyright © 2004, Oracle. All rights reserved.

Using LIST, n, and APPEND SQL> LIST 1 SELECT last_name 2* FROM employees SQL> 1 1* SELECT last_name SQL> A , job_id 1* SELECT last_name, job_id SQL> L 1 SELECT last_name, job_id 2* FROM employees Copyright © 2004, Oracle. All rights reserved.

Using the SAVE and START Commands SQL> L 1 SELECT last_name, manager_id, department_id 2* FROM employees SQL> SAVE my_query Created file my_query SQL> START my_query LAST_NAME MANAGER_ID DEPARTMENT_ID ------------------------- ---------- ------------- King 90 Kochhar 100 90 ... 20 rows selected. Copyright © 2004, Oracle. All rights reserved.

Summary In this appendix, you should have learned how to use SQL*Plus as an environment to do the following: • Execute SQL statements • Edit SQL statements • Format output • Interact with script files Copyright © 2004, Oracle. All rights reserved.

Oracle 10g sql fundamentals i

More Related Content

What's hot

Viewers also liked

Similar to Oracle 10g sql fundamentals i

Oracle 10g sql fundamentals i