Data Definition Language/ Data Description Language (DDL)

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 Introduction of DDL :

• It is a language that allows the users to define data and their relationship to other types of data.
• DDL is the short form of Data Definition Language, which deals with database schema and description of how the data should reside in the database.
• It is mainly used to create files, database, data dictionary and table within database.
• DDL can be used to define the conceptual/ Global/ Logical schema.
• A DDL is a language used to define data structures and modify data.

Following are the commands of DDL :

 CREATE :

It is used to create object in the database. The CREATE command can be used to establish each of these database on your platform.

ALTER :

It alters the structure of the database. The ALTER command allows you to make changes to the structure of a table without deleting and recreating it.

Drop :

Delete object from the database. The final command of the Data Definition Language, DROP, allows us to remove entire database objects from our DBMS.

For example

DROP TABLE personal_info

DROP DATABASE employees

TRUNCATE :    

Remove all records from a table, including all space allocated for the record are removed.

COMMENT :

Add comment to the data dictionary.

RENAME :

Rename an object.