What Is SQL? › Why SQL › What Can SQL Do?

What Can SQL Do?

You can use SQL to:

• Define a database
• Manipulate data in the database
• Control access to data in the database in a multi-user environment

Data Definition

You use SQL data description language (DDL) statements to define a database and tables within the database.

Data Manipulation

You use SQL DML statements to manipulate the data in tables.

There are four basic SQL DML statements:

• SELECT
• INSERT
• UPDATE
• DELETE

The SELECT statement is used to retrieve data. The result of a query is a result table. INSERT, UPDATE, and DELETE (all called update operations) are used to make changes to the data.

Data Control

You use SQL DDL to control access to data in a multi-user environment. There are two basic SQL DDL commands:

• GRANT
• REVOKE

The GRANT command allows another user to access data and the REVOKE command removes that access.

If you cannot access a table, it probably means that you have not been granted access to it.