ALTER TABLE Statements
Use the ALTER TABLE statement to add, delete, or modify the columns of a table.
ALTER TABLE Syntax
To add, delete, or modify columns, use the ADD, ALTER, or DROP keywords of the ALTER TABLE statement. The ADD keyword accepts a column definition or a comma-separated list of column definitions. The ALTER keyword accepts a column definition. The DROP keyword accepts a column name.
ALTER TABLE <table_name>
ADD [ COLUMN ] [ IF NOT EXISTS ]
<column_definition> | ( <column_definition> [ , ... ] )
| ALTER COLUMN <column_definition>
| DROP COLUMN [ IF EXISTS ] <column_name>
<column_definition> ::=
<column_name>
<data_type>
[ NOT NULL ]
[ DEFAULT <literal> ]
[ PRIMARY KEY ]
[ UNIQUE ]
Example Queries:
The following query adds a new ExternalCustomerId column on the server:
ALTER TABLE MyCustomers ADD (ExternalCustomerId int)
The following query changes the data type of the ExternalCustomerId column:
ALTER TABLE MyCustomers ALTER COLUMN ExternalCustomerId string
The following query removes the ExternalCustomerId column:
ALTER TABLE MyCustomers DROP COLUMN ExternalCustomerId