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ALTER DOMAIN

Name

ALTER DOMAIN --  change the definition of a domain

Synopsis

ALTER DOMAIN name
    { SET DEFAULT expression | DROP DEFAULT }
ALTER DOMAIN name
    { SET | DROP } NOT NULL
ALTER DOMAIN name
    ADD domain_constraint
ALTER DOMAIN name
    DROP CONSTRAINT constraint_name [ RESTRICT | CASCADE ]
ALTER DOMAIN name
    OWNER TO new_owner 
ALTER DOMAIN name
    SET SCHEMA new_schema 

Description

ALTER DOMAIN changes the definition of an existing domain. There are several sub-forms:

SET/DROP DEFAULT

These forms set or remove the default value for a domain. Note that defaults only apply to subsequent INSERT commands; they do not affect rows already in a table using the domain.

SET/DROP NOT NULL

These forms change whether a domain is marked to allow NULL values or to reject NULL values. You can only SET NOT NULL when the columns using the domain contain no null values.

ADD domain_constraint

This form adds a new constraint to a domain using the same syntax as CREATE DOMAIN. This will only succeed if all columns using the domain satisfy the new constraint.

DROP CONSTRAINT

This form drops constraints on a domain.

OWNER

This form changes the owner of the domain to the specified user.

SET SCHEMA

This form changes the schema of the domain. Any constraints associated with the domain are moved into the new schema as well.

You must own the domain to use ALTER DOMAIN. To change the schema of a domain, you must also have CREATE privilege on the new schema. To alter the owner, you must also be a direct or indirect member of the new owning role, and that role must have CREATE privilege on the domain's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the domain. However, a superuser can alter ownership of any domain anyway.)

Parameters

name

The name (possibly schema-qualified) of an existing domain to alter.

domain_constraint

New domain constraint for the domain.

constraint_name

Name of an existing constraint to drop.

CASCADE

Automatically drop objects that depend on the constraint.

RESTRICT

Refuse to drop the constraint if there are any dependent objects. This is the default behavior.

new_owner

The user name of the new owner of the domain.

new_schema

The new schema for the domain.

Notes

Currently, ALTER DOMAIN ADD CONSTRAINT and ALTER DOMAIN SET NOT NULL will fail if the named domain or any derived domain is used within a composite-type column of any table in the database. They should eventually be improved to be able to verify the new constraint for such nested columns.

Examples

To add a NOT NULL constraint to a domain:

ALTER DOMAIN zipcode SET NOT NULL;

To remove a NOT NULL constraint from a domain:

ALTER DOMAIN zipcode DROP NOT NULL;

To add a check constraint to a domain:

ALTER DOMAIN zipcode ADD CONSTRAINT zipchk CHECK (char_length(VALUE) = 5);

To remove a check constraint from a domain:

ALTER DOMAIN zipcode DROP CONSTRAINT zipchk;

To move the domain into a different schema:

ALTER DOMAIN zipcode SET SCHEMA customers;

Compatibility

ALTER DOMAIN conforms to the SQL standard, except for the OWNER and SET SCHEMA variants, which are PostgreSQL extensions.

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