Creating Constraints¶

A constraint can be created at table creation using CREATE TABLE, or added to a table later using ALTER TABLE:

Single-column constraints can be created inline as part of the column definition.
Multi-column constraints must be created in a separate, i.e. out-of-line, clause that specifies the columns in the constraint.

To create a constraint, certain access control privileges must be granted on the role used to create the constraint. For more information, see the security details described in Additional Constraint Details.

In this Topic:

Creating Constraints Inline
Creating Constraints Out-of-line

Creating Constraints Inline¶

The following inline syntax can only be used for single-column constraints:

CREATE [OR REPLACE] TABLE <name> (<column_name> <column_type> [ <inline_constraint> ], ... )

ALTER TABLE <name> ADD COLUMN <column_name> <column_type> [ <inline_constraint> ]

For inline_constraint syntax details, see CREATE | ALTER TABLE … CONSTRAINT.

Creating Constraints Out-of-line¶

The following out-of-line syntax must be used for multi-column constraints, but can also be used for single-column constraints:

CREATE [OR REPLACE] TABLE <name> ( ... , [ <outofline_constraint> ], ... )

ALTER TABLE <name> ADD <outofline_constraint>

For outofline_constraint syntax details, see CREATE | ALTER TABLE … CONSTRAINT.