Difference between revisions of "NOT NULL Column Constraint"

Revision as of 04:17, 25 October 2011

Purpose

Column constraint to disallow NULL values

Syntax

NOT NULL

See Also

ALTER TABLE, CONSTRAINTS, CREATE TABLE

Description

A constraint is used to define rules that help to provide data integrity. Column constraints are specific to the column name specified. You must have ALTER privilege on the table. The table will be locked for EXCLUSIVE use during the operation.

The NOT NULL column constraint is used to specify that the column cannot contain NULL values. The NULL column constraint can be used to allow NULL values.

Example

ALTER TABLE customer;
  ADD COLUMN custref CHAR(5) NULL
ALTER TABLE customer;
  ALTER COLUMN custref NOT NULL

Products

Recital, Recital Server