The SQL ALTER statement is used to add, modify, or delete fields in an existing database table.

Employees Table

employeeID	employeeName	accountCreated
1000	John Smith	1995-12-03 13:23:30.657
1001	Fred White	2001-10-12 09:41:44.125
1002	Jane Scott	1998-05-01 11:36:16.334
1003	Samuel Williams	1991-01-03 15:19:51.293

Syntax

ALTER TABLE tableName ADD columnName dataType

ALTER TABLE tableName ALTER COLUMN columnName dataType

ALTER TABLE tableName DROP COLUMN columnName

Example

ALTER TABLE Employees DROP COLUMN accountCreated

Results

employeeID	employeeName
1000	John Smith
1001	Fred White
1002	Jane Scott
1003	Samuel Williams

The ALTER Statement used in this example deleted the 'accountCreated' field by using the DROP keyword in the statement.

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