☞ SQL statements are classified into the following categories :
1. Data Definition Language (DDL) 2. Data Manipulation Language (DML) 3. Data Query Language (DQL) 4. Data Control Language (DCL) 5. Transaction Control Language (TCL)Note : We shall be discussing only DDL and DML commands as per the syllabus.
☞ It permits the database tables to be created or deleted i.e. it defines the structure of table.
☞ It also defines indices(keys), specifies link between tables and imposes constraints on tables.
☞ It contains the necessary statements for creating, manipulating, altering and deleting the table.
☞ Following are the DDL commands
1. CREATE 2. ALTER 3. DROP
☞ It helps a user to access or manipulate data.
☞ Following are the DML commands
1. INSERT 2. DELETE 3. UPDATE
☞ It is used to retrieve a subset of records from one or more tables.
☞ Following is the DQL command
1. SELECT