SQL guide-ALTER TABLE

ALTER TABLE

The alter table statement is used to add and delete columns in an existing table.

ALTER TABLE table_name ADD column_name datatype ALTER TABLE table_name DROP COLUMN column_name

Note:Some database systems cannot delete columns in data tables (drop column column_name)

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Person:

Lastname	Firstname	Address
Pettersen	Kari	Storgt 20

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Example

Add a column named "city" to the "person" table.

ALTER TABLE Person ADD City varchar(30)

Returned results

Lastname	Firstname	Address	City
Pettersen	Kari	Storgt 20

Example

Delete the "Address" column from the "person" table.

ALTER TABLE Person DROP COLUMN Address

Returned results

Lastname	Firstname	City
Pettersen	Kari