SQL & Adv SQL - Basics and Advanced for Beginners

SQL & ADVANCED SQL Marcin Blaszczyk (CERN IT-DB) marcin.blaszczyk@cern.ch

 Goal of this tutorial:  Present the overview of basic SQL capabilities  Explain several selected advanced SQL features  Outline  Introduction  SQL basics  Joins & Complex queries  Analytical functions & Set operators  Other DB objects (Sequences, Synonyms, DBlinks, Views & Mviews)  Indexes & IOTs  Partitioning  Undo & Flashback technologies AGENDA Oracle Tutorials 5th of May 2012

 Objective: be able to perform the basic operation of the RDBMS data model  create, modify the layout of a table  remove a table from the user schema  insert data into the table  retrieve and manipulate data from one or more tables  update/ delete data in a table  +  Some more advanced modifications SQL LANGUAGE Oracle Tutorials 5th of May 2012

 Structured Query Language  Programing language  Designed to mange data in relational databases  DDL Data Definition Language  Creating, replacing, altering, and dropping objects  Example: DROP TABLE [TABLE];  DML Data Modification Language  Inserting, updating, and deleting rows in a table  Example: DELETE FROM [TABLE];  DCL Data Control Language  Controlling access to the database and its objects  Example: GRANT SELECT ON [TABLE] TO [USER]; SQL LANGUAGE (2) Oracle Tutorials 5th of May 2012

STATEMENT DESCRIPTION SELECT Data Retrieval INSERT UPDATE DELETE Data Manipulation Language (DML) CREATE ALTER DROP RENAME TRUNCATE Data Definition Language (DDL) GRANT REVOKE Data Control Language (DCL) COMMIT ROLLBACK Transaction Control Oracle Tutorials SQL LANGUAGE(3) 5th of May 2012

 A transaction is a sequence of SQL Statements that Oracle treats as a single unit of work  A transaction must be commited or rolled back: COMMIT; - makes permanent the database changes you made during the transaction. ROLLBACK; - ends the current transaction and undoes any changes made since the transaction began.  Check COMMIT settings in your Client Tool (eg AUTOCOMMIT, EXITCOMMIT in SQL*Plus)  UNDO tablespace:  circular buffer  records all actions of transactions  used when rolling back a transaction Oracle Tutorials TRANSACTION & UNDO 5th of May 2012

 Collection of logical structures of data  called schema objects  tables, views, indexes, synonyms, sequences, packages, triggers, links, …  Owned by a database user  same name of the user  Schema objects can be created and manipulated with SQL SELECT * FROM USER_OBJECTS | USER_TABLES (…) SELECT user DROM dual; SHOW USER; (in SQL*Plus) DATABASE SCHEMA (USER) Oracle Tutorials 5th of May 2012

 Define the table layout:  table identifier  column identifiers and data types  column constraints,  default values  integrity constraints  relational constraints CREATE A TABLE Oracle Tutorials CREATE TABLE employees ( employee_id NUMBER(6) NOT NULL, first_name VARCHAR2(20), last_name VARCHAR2(25), hire_date DATE DEFAULT SYSDATE, department_id NUMBER(4), salary NUMBER(8,2) CHECK (salary > 0)); SQL> describe employees Name Null? Type ----------------- -------- ------------ EMPLOYEE_ID NOT NULL NUMBER(6) FIRST_NAME VARCHAR2(20) LAST_NAME VARCHAR2(25) HIRE_DATE DATE DEPARTMENT_ID NUMBER(4) SALARY NUMBER(8,2) 5th of May 2012

 Each value has a datatype  defines the domain of values that each column can contain  when you create a table, you must specify a datatype for each of its columns  ANSI defines a common set  Oracle has its set of built-in types  User-defined types DATATYPES Oracle Tutorials ANSI data type Oracle integer NUMBER(38) smallint NUMBER(38) numeric(p,s) NUMBER(p,s) varchar(n) VARCHAR2(n) char(n) CHAR(n) float NUMBER real NUMBER 5th of May 2012

SELECT [ALL | DISTINCT] column1[,column2] FROM table1[,table2] [WHERE "conditions"] [GROUP BY "column-list"] [HAVING "conditions] [ORDER BY "column-list" [ASC | DESC] ] Oracle Tutorials SELECT STATEMENT SELECT d.department_name, sum(e.salary)as DEPT_AL FROM departments d, employees e WHERE d.department_id = e.department_id GROUP BY d.department_name HAVING SUM(e.salary) > 10000 ORDER BY department_name; DEPARTMENT_NAME DEPT_SAL -------------------- ---------- Accounting 20300 Executive 58000 Finance 51600 IT 28800 Marketing 19000 Purchasing 24900 Sales 304500 Shipping 156400 5th of May 2012

 Insert some data INSERT INTO table1 values(value-list) ; INSERT INTO table1(column-list) values(value-list); INSERT INTO table1(column-list) SELECT values(value-list); COMMIT;  Update UPDATE table1 SET column = value; COMMIT;  Delete DELETE FROM table1; COMMIT; INSERT, UPDATE, DELETE (DML) Oracle Tutorials 5th of May 2012

 Modify the name: ALTER TABLE employees RENAME TO newemployees;  Modify the layout: ALTER TABLE employees ADD (salary NUMBER(7)); ALTER TABLE employees RENAME COLUMN id TO emp_id; ALTER TABLE employees DROP(hiredate);  But also:  Add/modify/drop constraints  Enable/Disable constraints  Modify more advanced properties… ALTER TABLE (DDL) Oracle Tutorials 5th of May 2012

 NOT NULL / CHECK ALTER TABLE employees MODIFY last_name NOT NULL; ALTER TABLE employees MODIFY salary CHECK (salary > 1000);  PRIMARY KEY ALTER TABLE employees ADD PRIMARY KEY(emp_id);  FOREIGN KEY ALTER TABLE employees ADD FOREIGN KEY(dept_id) REFERENCES departments(department_id);  Constraints errors:  ORA-02290: check constraint (owner.constraintname) violated – DURING INSERT  ORA-02291: integrity constraint (owner.constraintname) violated - parent key not found – DURING INSERT  ORA-02292:violated integrity constraint (owner.constraintname)- child record found – DURING DELETE CONSTRAINTS (DDL) Oracle Tutorials 5th of May 2012

 special value that means  unavailable  unassigned  unknown  inapplicable  not equivalent to  zero  blank space SELECT * FROM [TABLE] where id = 0; SELECT * FROM [TABLE] where id IS NULL;  Often used as default NULL VALUE Oracle Tutorials 5th of May 2012

 special one-row table present by default in all Oracle database installations  Accessible to all users  Examples of use: SELECT SYSDATE FROM DUAL; SELECT USER FROM DUAL; -- equal to SHOW USER in SQL*Plus  Create really big table in one command - use dual; CREATE TABLE BIG_TABLE AS SELECT trunc(dbms_random.value(0,20)) RANDOM_INT FROM DUAL CONNECT BY LEVEL <= 100000; DUAL TABLE Oracle Tutorials SQL> describe dual; Name Null? Type ----------------- -------- ------------ DUMMY VARCHAR2(1) 5th of May 2012

 ?  What is the difference between: DELETE FROM employees; vs TRUNCATE TABLE employees;  DML vs DDL commands?  Is COMMIT essential? In which case?  Generate UNDO segments?  Which is more efficient? DELETE ALL ROWS FROM A TABLE Oracle Tutorials 5th of May 2012

EQUIJOIN Values in the two corresponding columns of the different tables must be equal NON-EQUIJOIN The relationship between the columns of the different tables must be other than equal OUTERJOIN (LEFT, RIGHT, FULL) It returns also the rows that do not satisfy the join condition SELFJOIN Joining data in a table to itself TYPES OF JOINS Oracle Tutorials 5th of May 2012

EQUIJOIN Oracle Tutorials EMP_NAME EMP_DEPTNO KING 10 BLAKE 30 CLARK 10 DEPT_NO DEPT_NAME 10 ACCOUNTING 30 SALES 20 OPERATIONS EMP_NAME EMP_DEPTNO DEPT_NAME KING 10 ACCOUNTING BLAKE 30 SALES CLARK 10 ACCOUNTING 5th of May 2012 SQL> SELECT e.emp_name, e.emp_deptno, d.dept_name FROM emp e, dept d WHERE e.emp_deptno = d.deptno ORDER BY emp_name;

OUTERJOIN Oracle Tutorials EMP_NAME EMP_DEPTNO KING 10 BLAKE NULL CLARK 10 MARTIN 20 TURNER 10 JONES NULL DEPT_NO DEPT_NAME 10 ACCOUNTING 30 SALES 20 OPERATIONS EMP_NAME EMP_DEPTNO DEPT_NAME KING 10 ACCOUNTING BLAKE NULL NULL CLARK 10 ACCOUNTING MARTIN 20 OPERATIONS TURNER 10 ACCOUNTING JONES NULL NULL 5th of May 2012 SQL> SELECT e.emp_name, e.emp_deptno, d.dept_name FROM emp e, dept d WHERE e.emp_deptno = d.deptno(+) ORDER BY emp_name;

 Equijoins:  ANSI syntax SELECT e.name, d.name FROM employees e INNER JOIN departments d ON e.dept_id=d.dept_id;  Oracle SELECT e.name, d.name FROM employees e, departments d WHERE e.dept_id=d.dept_id;  Outerjoins  ANSI syntax (LEFT, RIGHT, FULL) SELECT e.name, d.name FROM employees e RIGHT OUTER JOIN departments d ON e.dept_id=d.dept_id;  Oracle SELECT e.name, d.name FROM employees e, departments d WHERE e.dept_id(+)=d.dept_id; JOINS SYNTAX ANSI VS ORACLE Oracle Tutorials 5th of May 2012

Types Question SUBQUERIES Who works in the same department as Clark? Correlated SUBQUERIES Who are the employees that receive more than the average salary of their department? Inline Views What are the employees salary and the minimum salary in their department? Top-N QUERIES What are the 5 most well paid employees? Hierarchical QUERIES What is the hierarchy of management in my enterprise? ADVANCED SQL QUERIES Oracle Tutorials 5th of May 2012

 A subquery is a query within a query and it is used to answer multiple-part questions.  Oracle fully supports them in the sense that:  You can create subqueries within your SQL statements  A subquery can reside in the WHERE clause, the FROM clause or the SELECT clause. Subquery Inline view Nested subquery SELECT ... FROM ... WHERE ... SUBQUERIES (1/5) Oracle Tutorials 5th of May 2012

SUBQUERIES (2/5) Oracle Tutorials A) Single-row (and single-column) B) Multiple-row (and single-column) C) Multiple-column  who works in the same department as Clark? SELECT … WHERE dep = (SELECT dep FROM … WHERE name = ‘CLARK’);  who works in the same department as Clark OR Blake? SELECT … WHERE dep IN (SELECT dep FROM … WHERE name =‘CLARK’ or name = ‘BLAKE’);  who works in the same department(s) AND under the same boss as Clark? SELECT … WHERE (dep, mgr) = (SELECT dep, mgr FROM … WHERE name = ‘CLARK’) Types 5th of May 2012

 A correlated subquery is a subquery that is evaluated FOR EACH ROW produced by the parent query.  Which employees receive more than the average salary of their department?  In this case, the correlated subquery specifically computes, for each employee, the average salary for the employee’s department CORRELATED SUBQUERIES Oracle Tutorials SELECT e.emp_id, e.dept_id, e.last_name, e.salary FROM employees e WHERE e.salary > (SELECT avg(i.salary) FROM employees i WHERE e.dept_id = i.dept_id) EMP_ID DEPT_ID LAST_NAME SALARY ------ ------- ---------- ------ 201 20 Hartstein 13000 114 30 Raphaely 11000 123 50 Vollman 6500 122 50 Kaufling 7900 120 50 Weiss 8000 121 50 Fripp 8200 103 60 Hunold 9000 147 80 Errazuriz 12000 146 80 Partners 13500 145 80 Russell 14000 100 90 King 24000 108 100 Greenberg 12000 5th of May 2012

 An In-line view is a subquery in the FROM clause of a SQL statement just as if it was a table. It acts as a data source!  What are the employees salary and the MINIMAL salary in their department? INLINE VIEWS Oracle Tutorials SELECT e.emp_id a.dept_id, e.last_name, e.salary, a.min_sal, FROM employees e, (SELECT MIN(salary)min_sal, dept_id FROM employees GROUP BY dept_id) a WHERE e.dept_id = a.dept_id ORDER BY e.dept_id, e.salary DESC; EMP_ID DEPT_ID LAST_NAME SALARY MIN_SAL ------ ------- ----------- ------ ------- 200 10 Whalen 4400 4400 201 20 Hartstein 13000 6000 202 20 Fay 6000 6000 114 30 Raphaely 11000 2500 115 30 Khoo 3100 2500 116 30 Baida 2900 2500 117 30 Tobias 2800 2500 118 30 Himuro 2600 2500 119 30 Colmenares 2500 2500 203 40 Mavris 6500 6500 121 50 Fripp 8200 2100 120 50 Weiss 8000 2100 122 50 Kaufling 7900 2100 123 50 Vollman 6500 2100 124 50 Mourgos 5800 2100 184 50 Sarchand 4200 2100 185 50 Bull 4100 2100 192 50 Bell 4000 2100 5th of May 2012

 We need to use “in-line view” together with the ROWNUM pseudocolumn  What are the top 5 most well paid employees?  What are the next 5 most well paid employees? TOP-N QUERIES Oracle Tutorials SELECT * FROM (SELECT emp_id, last_name, salary FROM employees ORDER BY salary desc) WHERE rownum < 6 EMP_ID LAST_NAME SALARY ------ ---------- ------ 100 King 24000 101 Kochhar 17000 102 De Haan 17000 145 Russell 14000 146 Partners 13500 SELECT emp_id, last_name, salary FROM ( SELECT emp_id,last_name, salary, rownum as rnum FROM employees ORDER BY salary desc) WHERE rnum between 6 and 10; EMP_ID LAST_NAME SALARY ------ ---------- ------ 108 Greenberg 12000 109 Faviet 9000 106 Pataballa 4800 105 Austin 4800 107 Lorentz 4200 5th of May 2012

 If a table contains hierarchical data, then you can select rows in a hierarchical order using the hierarchical query clause  Syntax:  Pseudo-column LEVEL is the hierarchy level HIERARCHICAL QUERIES Oracle Tutorials SELECT … FROM … WHERE … START WITH <condition> Specifies the starting point of the hierarchy (tree) CONNECT BY PRIOR child_row = parent_row (TOP-DOWN) parent_row = child_row (BOTTOM-UP) relationship between parent row and child rows of the hierarchy SELECT empid, last_name, mgrid, LEVEL FROM employees WHERE LEVEL <= 3 START WITH employee_id = 100 CONNECT BY PRIOR employee_id = manager_id; EMPID LAST_NAME MGRID LEVEL ----- --------- ----- ----- 100 King 1 101 Kochhar 100 2 200 Whalen 101 3 203 Mavris 101 3 204 Baer 101 3 Mavris King Kochnar Whalen Baer 5th of May 2012

 If a table contains hierarchical data, then you can select rows in a hierarchical order using the hierarchical query clause  Syntax:  Pseudo-column LEVEL is the hierarchy level HIERARCHICAL QUERIES Oracle Tutorials SELECT … FROM … WHERE … START WITH <condition> Specifies the starting point of the hierarchy (tree) CONNECT BY PRIOR child_row = parent_row (TOP-DOWN) parent_row = child_row (BOTTOM-UP) relationship between parent row and child rows of the hierarchy SELECT empid, last_name, mgrid, LEVEL FROM employees START WITH employee_id = 204 CONNECT BY PRIOR manager_id = employee_id; EMPID LAST_NAM MGR_ID LEVEL ----- -------- ------ ------ 204 Baer 101 1 101 Kochhar 100 2 100 King 3 Baer King Kochnar 5th of May 2012

 General syntax of analytical function: SELECT analytical-function(col-expr) OVER (window-spec) [AS col-alias] FROM [TABLE];  Window specification syntax [PARTITION BY [expr list]] ORDER BY [sort spec] [range spec]  Example for range specification (for more check oracle docs) ROWS UNBOUNDED PRECEDING AND CURRENT ROW (default) ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING RANGE BETWEEN 2 PRECEDING AND 2 FOLLOWING ANALYTICAL FUNCTIONS Oracle Tutorials EWWEQEWQEQ ASDASSDA CURRENT ROW WINDOW TABLE 5th of May 2012

 Analytical functions applied to all window rows  Remember about ordering inside the window ORDERRED ANALYTICAL WINDOW Oracle Tutorials SQL> select employee_id, last_name, manager_id, salary sum(salary) over (order by employee_id, last_name, salary) as cumulative from employees; EMPLOYEE_ID LAST_NAME MANAGER_ID SALARY CUMULATIVE ----------- --------- ---------- ------ ---------- 100 King 24000 24000 101 Kochhar 100 17000 41000 102 De Haan 100 17000 58000 = 24000+17000+17000 103 Hunold 102 9000 67000 104 Ernst 103 6000 73000 105 Austin 103 4800 77800 106 Pataballa 103 4800 82600 107 Lorentz 103 4200 86800 108 Greenberg 101 12000 98800 109 Faviet 108 9000 107800 110 Chen 108 8200 116000 5th of May 2012

RANGE SPECIFICATION (1/2) Oracle Tutorials  RANGE BETWEEN 2 PRECEDING AND 2 FOLLOWING SQL> select manager_id, last_name, salary, sum(salary) over (order by last_name, salary rows between 2 preceding and 1 following) as cumulative from employees; MANAGER_ID LAST_NAME SALARY CUMULATIVE ---------- --------- ------ ---------- 103 Austin 4800 10800 103 Ernst 6000 22800 101 Greenberg 12000 31800 102 Hunold 9000 51000 = 6000 + 12000 + 9000 + 24000 King 24000 62000 100 Kochhar 17000 54200 103 Lorentz 4200 45200 5th of May 2012

RANGE SPECIFICATION (2/2) Oracle Tutorials  ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING SQL> select manager_id, last_name, salary, sum(salary) over (order by last_name, salary rows between current row and unbounded following) as cumulative from emp_part; MANAGER_ID LAST_NAME SALARY CUMULATIVE ---------- --------- ------ ---------- 103 Austin 4800 77000 103 Ernst 6000 72200 101 Greenberg 12000 66200 102 Hunold 9000 54200 = 9000 + 24000 + 17000 + 4200 King 24000 45200 100 Kochhar 17000 21200 103 Lorentz 4200 4200 5th of May 2012

 Analytical functions start again for each partition PARTITIONED ANALYTICAL WINDOW Oracle Tutorials SQL> break on manager_id SQL> SELECT manager_id, last_name, employee_id, salary, sum(salary) over (PARTITION BY manager_id order by employee_id) as cumulative FROM employees order by manager_id, employee_id, last_name; MANAGER_ID LAST_NAME EMPLOYEE_ID SALARY CUMULATIVE ---------- --------------- ----------- ------ ---------- 100 Kochhar 101 17000 17000 De Haan 102 17000 34000 Raphaely 114 11000 45000 Weiss 120 8000 53000 101 Greenberg 108 12000 12000 Whalen 200 4400 16400 Mavris 203 6500 22900 Baer 204 10000 32900 102 Hunold 103 9000 9000 103 Ernst 104 6000 6000 Austin 105 4800 10800 Pataballa 106 4800 15600 5th of May 2012

 For analytic functions, you can use all of the regular group functions  SUM  MAX  MIN  AVG  COUNT  Plus list of additional analytical functions that can be used only for window queries.  LAG  LEAD  FIRST  LAST  FIRST VALUE  LAST VALUE  ROW_NUMBER  DENSE_RANK ANALYTIC FUNCTIONS Oracle Tutorials 5th of May 2012

 LAG function example ANALYTICAL FUNCTION EXAMPLE Oracle Tutorials SQL> select * from currency order by 1; DAY EURCHF -------------------- ------ 01-JUN-2012 00:00:00 1.240 02-JUN-2012 00:00:00 1.223 03-JUN-2012 00:00:00 1.228 04-JUN-2012 00:00:00 1.217 05-JUN-2012 00:00:00 1.255 06-JUN-2012 00:00:00 1.289 07-JUN-2012 00:00:00 1.291 08-JUN-2012 00:00:00 1.247 09-JUN-2012 00:00:00 1.217 10-JUN-2012 00:00:00 1.265 SQL> select day, EURCHF, lag(EURCHF,1) over (order by day) as prev_eurchf from currency; DAY EURCHF PREV_EURCHF -------------------- ------ -------------- 01-JUN-2012 00:00:00 1.240 02-JUN-2012 00:00:00 1.223 1.240 03-JUN-2012 00:00:00 1.228 1.223 04-JUN-2012 00:00:00 1.217 1.228 05-JUN-2012 00:00:00 1.255 1.217 06-JUN-2012 00:00:00 1.289 1.255 07-JUN-2012 00:00:00 1.291 1.289 08-JUN-2012 00:00:00 1.247 1.291 09-JUN-2012 00:00:00 1.217 1.247 10-JUN-2012 00:00:00 1.265 1.217 SQL> select day, EURCHF, ((EURCHF - prev_eurchf) / prev_eurchf )*100 as pct_change from ( select day, EURCHF, LAG(EURCHF,1) over (order by day) as prev_eurchf from currency); DAY EURCHF PCT_CHANGE -------------------- ------ ---------- 01-JUN-2012 00:00:00 1.240 02-JUN-2012 00:00:00 1.223 -1.37 03-JUN-2012 00:00:00 1.228 0.41 04-JUN-2012 00:00:00 1.217 -0.90 05-JUN-2012 00:00:00 1.255 3.12 06-JUN-2012 00:00:00 1.289 2.71 07-JUN-2012 00:00:00 1.291 0.16 08-JUN-2012 00:00:00 1.247 -3.41 09-JUN-2012 00:00:00 1.217 -2.41 10-JUN-2012 00:00:00 1.265 3.94 -1.37 0.41 -0.9 3.12 2.71 0.16 -3.41 -2.41 3.94 -4 -2 0 2 4 6 5th of May 2012

 Combine multiple queries  Union without duplicates SELECT name, email FROM employees UNION SELECT name, email FROM visitors;  Union with the duplicates SELECT cit_id FROM employees UNION ALL SELECT cit_id FROM visitors;  Intersect SELECT name FROM employees INTERSECT SELECT name FROM visitors;  Minus SELECT name FROM employees MINUS SELECT name FROM visitors; SET OPERATORS Oracle Tutorials 5th of May 2012

 A database object that generates (in/de)creasing unique integer numbers  Very efficient thanks to caching  Transaction safe  It is typically used to generate Primary Key values  No guarantee that ID will be continuous  rollback, use in >1 tables, concurrent sessions  Gaps less likely if caching switched off  The use of application-side generation of numbers is not recommended. Highly prone to locks, errors. SEQUENCES Oracle Tutorials SQL> CREATE SEQUENCE seq_dept INCREMENT BY 10 MAXVALUE 1000 NOCACHE; SELECT seq_dept.NEXTVAL FROM DUAL; SELECT seq_dept.CURRVAL FROM DUAL; INSERT INTO dept VALUES (seq_dept.NEXTVAL,‘HR’,4); 5th of May 2012

 object in the local database that allows you to access objects on a remote database CREATE DATABASE LINK devdb CONNECT TO scott IDENTIFIED BY tiger USING ‘devdb’;  How to access to tables over a database link? SELECT * FROM emp@devdb;  Solution: Use synonyms to hide the fact that a table is remote: CREATE SYNONYM emp_syn for emp@devdb; SELECT * FROM emp_syn; DATABASE LINKS & SYNONYMS Oracle Tutorials 5th of May 2012

 Special type of table for storing temporary data  Volatile – no statistics are gathered  Session or transaction  ON COMMIT PRESERVE | DELETE ROWS  indexes, views can be created on temporary tables TEMPORARY TABLES Oracle Tutorials SQL> CREATE GLOBAL TEMPORARY TABLE temp_table_session (id number) ON COMMIT PRESERVE ROWS; SQL> CREATE GLOBAL TEMPORARY TABLE temp_table_transaction (id number) ON COMMIT DELETE ROWS; SQL> INSERT INTO temp_table_session values(2); SQL> INSERT INTO temp_table_transaction values(2); SQL> COMMIT; SQL> SELECT * FROM temp_table_session; ID -------------- 2 SQL> SELECT * FROM temp_table_transaction; no rows selected 5th of May 2012

 It’s a stored SQL statement that defines a virtual table. It takes the output of a query and makes it appear as a virtual table  Advantages:  To hide the complexity of a query  Provide different representations of same data  To ensure that exactly the same SQL is used throughout your application  To improve security by restricting access to data  Restrict the columns/rows which can be queried  Restrict the rows and columns that may be modified  To isolate and application from any future change to the base table definition  Users formulate their queries on the views (virtual tables)  Views are updatable! Use WITH READ ONLY to make view nonupdatable VIEWS Oracle Tutorials 5th of May 2012

 Data dictionary? Read-only set of tables that provides information about the database  These predefined views provided by oracle are a source of valuable information for developers and dbusers DATA DICTIONARY VIEWS Oracle Tutorials user_ts_quotas user quotas per tablespace user_objects, user_tables, user_views, user_mviews user_indexes user_constraints objects created in the user’s schema user_sys_privs, user_role_privs, user_tab_privs system privileges roles granted to the user privileges granted on the user’s objects user_segments, user_extents storage of the user’s objects session_privs all privileges available for current session 5th of May 2012

 A database object that stores the result of a query  A hybrid of view and table  Advantages  Useful for summarizing, pre-computing, replicating and distributing data  Faster access for expensive and complex joins  Transparent to end-users  Especially useful for heavy queries and big tables  Disadvantages  Storage costs of maintaining the views  configuration for refresh MATERIALIZED VIEWS (1/2) Oracle Tutorials 5th of May 2012

 Syntax of materialized views: CREATE MATERIALIZED VIEW mv BUILD IMMEDIATE | DEFFERED | ON PREBUILT TABLE REFRESH COMPLETE | FAST | FORCE ON COMMIT | ON DEMAND | START WITH ENABLE QUERY REWRITE AS (SELECT… FROM tab1e);  The “query rewrite” feature – the ability of database engine to silently rewrites the query and executes it against MV.  Controlled by following Oracle parameters:  QUERY_REWRITE_ENABLED  QUERY_REWRITE_INTEGRITY MATERIALIZED VIEWS (2/2) Oracle Tutorials 5th of May 2012

 Index with a balanced tree  When to use? 1. OLTP systems 2. High cardinality columns (primary key columns) 3. Size: B-tree index will be signifficantly smaller than Bitmap index for high cardinality column. B-TREE INDEX Oracle Tutorials SELECT * FROM employee WHERE empid < 73 CREATE INDEX i_employee_id ON employee (empid); 5th of May 2012

 Index with a bitmap of the column values  When to use? 1. DSS systems (bitmap indexes can cause a serious locking problem in systems where data is frequently updated by many concurrent systems) 2. Low cardinality columns (columns with few discrete values) 3. Size: Bitmap index will be signifficantly smaller than B-tree index on low cardinality column BITMAP INDEX Oracle Tutorials SELECT * FROM employee WHERE sex=‘F’; CREATE BITMAP INDEX i_employee_sex ON employee (sex); 5th of May 2012

 Composite index: Index over multiple columns in a table  When to use?  When WHERE clause uses more than one column  To increase selectivity joining columns of low selectivity CREATE INDEX mgr_deptno_idx ON emp(mgr, deptno);  Function-based index: Is an index created on a function that involves columns in the table being indexed (b-tree or bitmap)  They speed up queries that evaluate those functions to select data because they pre-compute the result and stores it in an index CREATE INDEX emp_name_idx ON employee (UPPER(ename)); COMPOSITE & FUNCTION BASED IND Oracle Tutorials 5th of May 2012

 IOT stores all of the table’s data in the B-tree index structure CREATE TABLE orders ( order_id NUMBER(10), …, …, … CONSTRAINT pk_orders PRIMARY KEY (order_id) ) ORGANIZATION INDEX;  Efficient when:  table is usually accessed by the primary key  Inefficient when:  there’s a heavy DML activity especially not primary key based  access to table’s data not via primary key is slower comparing to a cheap table INDEX ORGANIZED TABLES Oracle Tutorials 5th of May 2012

 Tables and indexes can be divided into smaller and more manageable physical pieces called partitions which are treated as a single logical unit  Advantages:  Manageability: data management operations at the partition level (data load, index creation, backup/recovery, etc)  Performance: Improves query performance, possibility of concurrent maintenance operations on different partitions of the same table/index.  Partitioning can be implemented without requiring any modifications to your applications. ORACLE PARTITIONING Oracle Tutorials 5th of May 2012

 There are different criteria to split the data:  List: partition by lists of predefined discrete values  Range: partition by predefined ranges of continuous values  Hash: partition according to hashing algorithm applied by Oracle  Composite: e.g. range-partition by key1, hash-subpartition by key2 PARTITIONING TYPES Oracle Tutorials CREATE TABLE SALES_2010 ( salesman_id NUMBER(5), salesman_name VARCHAR2(30), region VARCHAR2(1), sales_amount NUMBER(10), sale_date DATE ) PARTITION BY RANGE(sale_date) ( PARTITION p_jan2010 VALUES LESS THAN(TO_DATE('01/01/2010','DD/MM/YYYY')), PARTITION p_feb2010 VALUES LESS THAN(TO_DATE('02/01/2010','DD/MM/YYYY')), PARTITION p_mar2010 VALUES LESS THAN(TO_DATE('03/01/2010','DD/MM/YYYY')), PARTITION p_apr2010 VALUES LESS THAN(TO_DATE('04/01/2010','DD/MM/YYYY')), (…) PARTITION p_aug2010 VALUES LESS THAN(TO_DATE('08/01/2010','DD/MM/YYYY')), PARTITION p_sep2010 VALUES LESS THAN(TO_DATE('09/01/2010','DD/MM/YYYY')), PARTITION p_oct2010 VALUES LESS THAN(TO_DATE('10/01/2010','DD/MM/YYYY')), PARTITION p_nov2010 VALUES LESS THAN(TO_DATE('11/01/2010','DD/MM/YYYY')), PARTITION p_dec2010 VALUES LESS THAN(TO_DATE('12/01/2010','DD/MM/YYYY')), PARTITION p_others VALUES LESS THAN (MAXVALUE)); 5th of May 2012

 There are different criteria to split the data:  List: partition by lists of predefined discrete values  Range: partition by predefined ranges of continuous values  Hash: partition according to hashing algorithm applied by Oracle  Composite: e.g. range-partition by key1, hash-subpartition by key2 PARTITIONING TYPES Oracle Tutorials CREATE TABLE SALES_REGIONS_2010 ( salesman_id NUMBER(5), salesman_name VARCHAR2(30), region VARCHAR2(1), sales_amount NUMBER(10), sale_date DATE ) PARTITION BY RANGE(sale_date) SUBPARTITION BY LIST(region) SUBPARTITION TEMPLATE ( SUBPARTITION p_emea VALUES ('E'), SUBPARTITION p_asia VALUES ('A'), SUBPARTITION p_nala VALUES ('N')) ( PARTITION p_jan2010 VALUES LESS THAN(TO_DATE('01/01/2010','DD/MM/YYYY')), PARTITION p_feb2010 VALUES LESS THAN(TO_DATE('02/01/2010','DD/MM/YYYY')), PARTITION p_mar2010 VALUES LESS THAN(TO_DATE('03/01/2010','DD/MM/YYYY')), (…) PARTITION p_nov2010 VALUES LESS THAN(TO_DATE('11/01/2010','DD/MM/YYYY')), PARTITION p_dec2010 VALUES LESS THAN(TO_DATE('12/01/2010','DD/MM/YYYY')), PARTITION p_others VALUES LESS THAN (MAXVALUE)); 5th of May 2012

 Table partitioned by date INSERT INTO table … VALUES(’MAR 2010’); SELECT * FROM table WHERE key = (’DEC 2010’); PARTITION PRUNNING Oracle Tutorials JAN2010 FEB2010 MAR2010 DEC2010 … JAN2010 FEB2010 MAR2010 DEC2010 … 5th of May 2012

PARTITION WISE JOINS Oracle Tutorials  Without partitioning: global join (query time ~ N x N)  With partitioning: local joins (query time ~ N) SELECT … FROM tab1, tab2 WHERE tab1.key = tab2.key JAN2010 FEB2010 MAR2010 DEC2010 … JAN2010 FEB2010 MAR2010 DEC2010 … tab1 JAN2010 FEB2010 MAR2010 DEC2010 … JAN2010 FEB2010 MAR2010 DEC2010 … tab2 tab1 tab2 join join 5th of May 2012

 Local index: partitioned on the same key as table CREATE INDEX day_idx ON table (day) LOCAL;  Global index: not partitioned on the same key as table CREATE INDEX day_idx ON table (day) GLOBAL;  Combine the advantages of partitioning and indexing:  Partitioning improves query performance by pruning  Local index improves performance on full scan of partition  Bitmap indexes on partitioned tables are always local  The concept of global index only applies to B*-tree indexes PARTITIONED INDEXES Oracle Tutorials 5th of May 2012

 For COMMITED data  Flashback technologies support recovery at all levels:  Row  Table  Transaction (this is not in the scope of this tutorial)  Entire Database (this is not in the scope of this tutorial)  We DO NOT GUARANTEE that past data will be always accessible (UNDO is a circular buffer)  SCN System Change Number - is an ever-increasing value that uniquely identifies a committed version of the database. In simple words: “it’s an Oracle's clock - every time we commit, the clock increments.” – Tom Kyte Oracle Tutorials FLASHBACK TECHNOLOGIES 5th of May 2012

 For error analysis  Flashback Query  Flashback Version query  Flashback Transaction query (not part of this tutorial)  For error recovery  Flashback Transaction Backout (not part of this tutorial) new 11g!  Flashback Table  Flashback Drop  Flashback Database (not part of this tutorial) Oracle Tutorials FLASHBACK TECHS (2) 5th of May 2012

 For analysis  To perform queries as of a certain time SELECT * FROM <TABLE> AS OF TIMESTAMP | SCN; Oracle Tutorials FLASHBACK QUERY SQL> SELECT * FROM test; no rows selected SQL> SELECT * FROM test AS OF SCN 6268302650456; ID STR_VAL -------------- ---------- 1 one 2 two 3 three SQL> select DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER from dual; GET_SYSTEM_CHANGE_NUMBER ------------------------ 6268302650456 SQL> delete from test; 3 rows deleted. SQL> commit; Commit complete. 5th of May 2012

 For analysis  To retrieve all the versions of the rows that exist between two points in time or two SCNs  Pseudocolumns:  VERSIONS_STARTTIME (start timestamp of version)  VERSIONS_ENDTIME (end timestamp of version)  VERSIONS_STARTSCN (start SCN of version)  VERSIONS_ENDSCN (end SCN of version)  VERSIONS_XID (transaction ID of version)  VERSIONS_OPERATION (DML operation of version)  The VERSIONS clause cannot span DDL commands SELECT versions_xid, versions_operation, salary FROM employees VERSIONS BEETWEN TIMESTAMP | SCN <t1> and <t2>; Oracle Tutorials FLASHBACK VERSION QUERY 5th of May 2012

 For error correction  Flashback Table provides a way for users to easily and quickly recover from accidental modifications without a database administrator’s involvement FLASHBACK TABLE employees TO TIMESTAMP | SCN <t1>; Oracle Tutorials FLASHBACK TABLE 5th of May 2012 SQL> SELECT * FROM test; no rows selected SQL> ALTER TABLE test ENABLE ROW MOVEMENT; Table altered. SQL> FLASHBACK ATBLE test TO SCN 6268302650456; Flashback complete. SQL> SELECT * FROM test ID STR_VAL -------------- ---------- 1 one 2 two 3 three

 For error correction  The RECYCLEBIN initialization parameter is used to control whether the Flashback Drop capability is turned ON or OFF.  It’s RECYCLEBIN is set to ON for CERN Physics databases FLASHBACK TABLE employees TO BEFORE DROP; Oracle Tutorials FLASHBACK DROP 5th of May 2012 SQL> DROP TABLE test; Table dropped. SQL> FLASHBACK TABLE test TO BEFORE DROP; Flashback complete.

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten select * from test; (as of scn 6268303136698) ID STR_VAL --- ---------- 1 one 9 nine 10 ten 11 eleven 5th of May 2012

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten select * from test; (as of scn 6268303136698) ID STR_VAL --- ---------- 1 one 9 nine 10 ten 11 eleven select * from test as of scn 6268303136686; ID STR_VAL --- ---------- 1 one 9 nine 5th of May 2012

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten select * from test; (as of scn 6268303136698) ID STR_VAL --- ---------- 1 one 9 nine 10 ten 11 eleven select * from test as of scn 6268303135869; ID STR_VAL --- ---------- 1 one 2 two 3 three select * from test as of scn 6268303136686; ID STR_VAL --- ---------- 1 one 9 nine 5th of May 2012

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten select * from test as of scn 6268303135869; ID STR_VAL --- ---------- 1 one 2 two 3 three create table test (id number(5), str_val varchar2(10)); insert into test values(1, 'one'); insert into test values(2, 'two'); insert into test values(3, 'three'); commit; 5th of May 2012

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten update test set id = 9, str_val = 'nine' where id =2; delete from test where id = 3; commit; select * from test as of scn 6268303136686; ID STR_VAL --- ---------- 1 one 9 nine 5th of May 2012

FLASHBACK Oracle Tutorials select versions_xid, versions_operation, versions_startscn, versions_endscn, id, str_val from test versions between timestamp minvalue and maxvalue order by VERSIONS_STARTSCN; VERSIONS_XID V VERSIONS_STARTSCN VERSIONS_ENDSCN ID STR_VAL ---------------- - ----------------- --------------- --- ---------- 21001D00F8B50F00 I 6268303135869 1 one 21001D00F8B50F00 I 6268303135869 6268303136686 3 three 21001D00F8B50F00 I 6268303135869 6268303136686 2 two 23000600BAFB0D00 U 6268303136686 9 nine 23000600BAFB0D00 D 6268303136686 3 three 23000400B9FC0D00 I 6268303136698 11 eleven 23000400B9FC0D00 I 6268303136698 10 ten insert into test values(10, 'ten'); insert into test values(11, 'eleven'); commit; select * from test; (as of scn 6268303136698) ID STR_VAL --- ---------- 1 one 9 nine 10 ten 11 eleven 5th of May 2012

 Oracle Documentation  http://www.oracle.com/pls/db112/homepage  SQL language reference  http://docs.oracle.com/cd/E11882_01/server.112/e26088/toc.htm  Mastering Oracle SQL and SQL*Plus, Lex De Haan  Oracle SQL Recipes, Allen Grant  Mastering Oracle SQL, Mishra Sanjay  Expert One on One Oracle, Thomas Kyte (more advanced topics than SQL) REFERENCES 5th of May 2012 Oracle Tutorials

QUESTIONS? THANK YOU! Marcin.Blaszczyk@cern.ch

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