ALTER DOMAIN
Synopsis
ALTER DOMAINname { SET DEFAULTexpression | DROP DEFAULT }ALTER DOMAINname { SET | DROP } NOT NULLALTER DOMAINname ADDdomain_constraint [ NOT VALID ]ALTER DOMAINname DROP CONSTRAINT [ IF EXISTS ]constraint_name [ RESTRICT | CASCADE ]ALTER DOMAINname RENAME CONSTRAINTconstraint_name TOnew_constraint_nameALTER DOMAINname VALIDATE CONSTRAINTconstraint_nameALTER DOMAINname OWNER TOnew_ownerALTER DOMAINname RENAME TOnew_nameALTER DOMAINname SET SCHEMAnew_schemaDescription
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 subsequentINSERT 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 onlySET NOT NULL when the columns using the domain contain no null values.
- ADDdomain_constraint [ NOT VALID ]
This form adds a new constraint to a domain using the same syntax asCREATE DOMAIN. When a new constraint is added to a domain, all columns using that domain will be checked against the newly added constraint. These checks can be suppressed by adding the new constraint using theNOT VALID option; the constraint can later be made valid usingALTER DOMAIN ... VALIDATE CONSTRAINT. Newly inserted or updated rows are always checked against all constraints, even those markedNOT VALID.NOT VALID is only accepted forCHECK constraints.
- DROP CONSTRAINT [ IF EXISTS ]
This form drops constraints on a domain. IfIF EXISTS is specified and the constraint does not exist, no error is thrown. In this case a notice is issued instead.
- RENAME CONSTRAINT
This form changes the name of a constraint on a domain.
- VALIDATE CONSTRAINT
This form validates a constraint previously added asNOT VALID, that is, verify that all data in columns using the domain satisfy the specified constraint.
- OWNER
This form changes the owner of the domain to the specified user.
- RENAME
This form changes the name of the domain.
- 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 useALTER DOMAIN. To change the schema of a domain, you must also haveCREATE 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 haveCREATE 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 or rename.
- NOT VALID
Do not verify existing column data for constraint validity.
- 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_name
The new name for the domain.
- new_constraint_name
The new name for the constraint.
- 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 andALTER 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 aNOT NULL constraint to a domain:
ALTER DOMAIN zipcode SET NOT NULL;
To remove aNOT 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 rename a check constraint on a domain:
ALTER DOMAIN zipcode RENAME CONSTRAINT zipchk TO zip_check;
To move the domain into a different schema:
ALTER DOMAIN zipcode SET SCHEMA customers;