ALTER TABLE

Use the ALTER TABLE statement to alter the structure of an existing database table; or to add or to delete an index. Its syntax is:

Action	Syntax
Add a column	ALTER TABLE table ADD COLUMN field type [(size)] [NOT NULL] [CONSTRAINT constraint]
Delete a column	ALTER TABLE table DROP COLUMN field
Add a table constraint	ALTER TABLE ADD CONSTRAINT constraint
Remove a constraint	ALTER TABLE DROP CONSTRAINT constraint

The parts of the above statements have the following meanings:

Part Meaning

table The name of the table to be altered.

field The name of tbe field to be added or removed from the table

type The data type of the field

size The field size in characters

constraint The constraint to be imposed or removed, expressed as a CONSTRAINT clause.

[Return to SQL Syntax]

Part	Meaning
table	The name of the table to be altered.
field	The name of tbe field to be added or removed from the table
type	The data type of the field
size	The field size in characters
constraint	The constraint to be imposed or removed, expressed as a CONSTRAINT clause.