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SQL ALTER TABLE

ALTER TABLE

The ALTER TABLE statement is used to add or drop 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 don't allow the dropping of a column in a database table (DROP COLUMN column_name).

Person:

LastName	FirstName	Address
Pettersen	Kari	Storgt 20

Example

To add a column named "City" in the "Person" table:

ALTER TABLE Person ADD City varchar(30)

Result:

LastName	FirstName	Address	City
Pettersen	Kari	Storgt 20

Example

To drop the "Address" column in the "Person" table:

ALTER TABLE Person DROP COLUMN Address

Result:

LastName	FirstName	City
Pettersen	Kari

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