Classification of SQL Statments

☞ 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.

Data Definition Language (DDL)

☞ 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

Data Manipulation Language (DML)

☞ It helps a user to access or manipulate data.

☞ Following are the DML commands

1. INSERT
2. DELETE
3. UPDATE

Data Query Language (DQL)

☞ It is used to retrieve a subset of records from one or more tables.

☞ Following is the DQL command

1. SELECT

Note : In some of the books SELECT command is given under the DML commands , so use it accordingly.