Database Basics and MySQL

Creation, Manipulation, and Management Jerome Locson Developer, Ariba Tech Solutions me@jeromelocson.com

 Graduate from ADZU, BSCS  PhilNITS FE Passer  GTUG PH, Zamboanga Chapter Community Manager  Technopreneur, Ariba Tech Solutions  Blog: www.jeromelocson.com

 Relational Database Concept  Structure Query Language (SQL) ◦ DDL, DML and DCL  Database Normalization  ACID Property  Relational Database Management Systems (RDBMS), MySQL  Example of MySQL Queries (PhpMyAdmin)  SQL Injection Prevention

◦ Used by all major commercial database systems ◦ Very simple model ◦ Query with high-level languages: simple yet expressive ◦ Efficient implementations

Schema = structural description of relations in database Instance = actual contents at given point in time

Database = set of named relations (or tables) Each relation has a set of named attributes (or columns) Each tuple (or row) has a value for each attribute Each attribute has a type (or domain)

NULL – special value for “unknown” or “undefined”

Key – attribute whose value is unique in each tuple Or set of attributes whose combined values are unique

 Standard/dominant language for accessing databases and processing  Steady improvements in reliability, performance and security  Applicable to many database systems

 It can define a database (DDL)  It can manipulate database (DML)  and, can control a database (DCL)

 defining the structure and contents of a relational database  Metadata (data about the data)  defines the mapping of database to physical hardware and devices  Basic Syntax: ◦ Create Table, Alter Table, Drop Table, Create View, Create User, etc.

 specifies how queries and updates are to be done  Basic Syntax: ◦ Select, Insert, Delete, Update

 involves configuring and controlling the database - permission, roles, and referential integrity  Basic Syntax: ◦ Grant, Check, Constraint, Primary Key, Foreign Key

 Process of efficiently organizing data in a database (1NF-5NF)  Too: Entity-Relationship Diagram (ERD)  Goals: ◦ eliminating redundant data ◦ ensuring data dependencies make sense  Forms: ◦ 1NF (First Normal Form) ◦ 2NF (Second Normal Form) ◦ 3NF (Third Normal Form)

 First normal form (1NF) sets the very basic rules for an organized database: ◦ Eliminate duplicative columns from the same table. ◦ Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).

 Second normal form (2NF) further addresses the concept of removing duplicative data: ◦ Meet all the requirements of the first normal form. ◦ Remove subsets of data that apply to multiple rows of a table and place them in separate tables. ◦ Create relationships between these new tables and their predecessors through the use of foreign keys.

 Third normal form (3NF) goes one large step further: ◦ Meet all the requirements of the second normal form. ◦ Remove columns that are not dependent upon the primary key.

 Stands for atomicity, consistency, isolation, durability  set of properties that guarantee database transactions are processed reliably

 Atomicity (atomic) ◦ requires that database modifications must follow an "all or nothing" rule ◦ If one part of the transaction fails, the entire transaction fails and the database state is left unchanged.

 Consistency ◦ ensures that any transaction the database performs will take it from one consistent state to another ◦ only consistent (valid according to all the rules defined) data will be written to the database ◦ whatever rows will be affected by the transaction will remain consistent with each and every rule

 Isolation ◦ no transaction should be able to interfere with another transaction at all ◦ use a serial model where no two transactions can occur on the same data at the same time

 Durability ◦ once a transaction has been committed, it will remain so ◦ every committed transaction is protected against power loss/crash/errors and cannot be lost by the system and can thus be guaranteed to be completed

 RDBMS is the basis for SQL, and for all modern database systems like MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.  MySQL database is the world's most popular open source database for the Web  Supports different languages, environment, etc.  www.mysql.com

• mysql_connect(host, username [,password]); ◦ Connects to a MySQL server on the specified host using the given username and/or password. Returns a MySQL link identifier on success, or FALSE on failure. • mysql_select_db(db_name [,resource]) ◦ Selects a database from the database server.

• mysql_query(SQL, resource); ◦ Sends the specified SQL query to the database specified by the resource identifier. The retrieved data are returned by the function as a MySQL result set. • mysql_result(result, row [,field]); ◦ Returns the contents of one cell from a MySQL result set. The field argument can be the field name or the field’s offset. • mysql_fetch_array(result [,result_type]) ◦ Fetch a result row as an associative array, a numeric array, or both. The result type can take the constants MYSQL_ASSOC, MYSQL_NUM, and MYSQL_BOTH.

• mysql_free_result(result) ◦ Frees the result set • mysql_close(resource) ◦ Closes the connection to the database.

 If there is error in the database connection, you can terminate the current script by using the die function.  For example: $db = mysql_connect("localhost", "root“, “”) or die("Could not connect : " . mysql_error()); mysql_select_db("my_database") or die("Could not select database"); $result = mysql_query($query) or die("Query failed");

<?php /* Connecting, selecting database */ $link = mysql_connect("mysql_host", "mysql_user", mysql_password") or die("Could not connect : " . mysql_error()); echo "Connected successfully"; mysql_select_db("my_database") or die("Could not select database"); /* Performing SQL query */ $query = "SELECT * FROM my_table"; $result = mysql_query($query) Loop through each row or die("Query failed : " . mysql_error()); of the result set /* Printing results in HTML */ echo "<table>n"; while ($line = mysql_fetch_array($result, MYSQL_ASSOC)) { echo "t<tr>n"; foreach ($line as $col_value) { Loop through each echo "tt<td>$col_value</td>n"; element in a row } echo "t</tr>n"; }

/* Free resultset */ mysql_free_result($result); /* Closing connection */ mysql_close($link); ?>

 Using mysql_real_escape_string()  Using of string replace method for SQL keywords like SELECT, INSERT, DELETE and UPDATE

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