Data Definition Language explains the part of SQL which allows creating, changing or altering and demolishing the database. The database includes different tables, sequences, catalogs, indexes etc. The commands are implemented by the supervisor of the system. The implementation takes place at the time of setup of the database and at the time of removal of the databases.

There are four basic DDL commands namely, Create, Use, Alter and Drop. Four of these are explained in detail as under:

Create

The database management system or DBMS, permit in creating and managing different databases. For e.g. If the company wants to maintain the database for the employees of the company the Create command is implemented for the same. The command would be: Create Database “Employees”. This command will create the database with the title “Employees”. After the database is created the next step is to create tables having the employee’s data in detail. The details would be: First name, last name and employee id.

Use

This command allows the user to work and use any specific command. The command would be “Use employees”.

Alter

After creating the table in the database, if the user need to change or edit the details a little bit it is possible with the Alter command. The changes can be done without deleting and re-creating the structure of the table. For e.g. “Alter Table Employee personal info, Add attendance record. The following example will enable the Employee’s attendance record table to be added in the master table.

Drop

This command is to remove the table or any kind of data from the database. According to the following e.g. “Drop Table Personal Info”. Similarly, the command can be used effectively for any particular task. This command should be used in an effective manner as the details to be deleted from the database are deleted automatically from the database after giving the Drop command.

The basic idea behind using the above mentioned command is to use the data effectively and on right position and right time.