Explain the different types of SQL commands.

Answer

• Data Definition Language: DDL is that part of SQL which defines the data structure of the database in the initial stage when the database is about to be created. It is mainly used to create and restructure database objects. Commands in DDL are:Data Manipulation Language: DML is used to manipulate the already existing data in the database. That is, it helps users retrieve and manipulate the data. It is used to perform operations such as inserting data into the database through the insert command, updating the data with the update command, and deleting the data from the database through the delete command.
  • Create table
  • Alter table
  • Drop table
• Data Control Language: DCL is used to control access to the data in the database. DCL commands are normally used to create objects related to user access and also to control the distribution of privileges among users. The commands that are used in DCL are Grant and Revoke.
• Transaction Control Language: It is used to control the changes made by DML commands. It also authorizes the statements to assemble in conjunction into logical transactions. The commands that are used in TCL are Commit, Rollback, Savepoint, Begin, and Transaction.