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Alter table command, Database Management System

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ALTER TABLE Command: This command is used for variation of existing structure of the table in the given situation:

  • When a new column is to be added to the table structure.
  • When the existing column definition has to be altered, i.e., changing the width of the data type or the data type itself.
  • When integrity constraints have to be dropped or included.
  • When a constraint has to be allowed or not allowed.

Syntax

ALTER TABLE

ADD ( ...); ALTER TABLE
MODIFY ( ...);

ALTER TABLE

ADD CONSTRAINT < constraint type>(field name);

ALTER TABLE

DROP;

ALTER TABLE

ENABLE/DISABLE ;

You require to put many constraints like that the database integrity is not compromised.

 

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