ALTER_DOMAIN - change the definition of a domain
ALTER DOMAIN name
{ SET DEFAULT expression | DROP DEFAULT }
ALTER DOMAIN name
{ SET | DROP } NOT NULL
ALTER DOMAIN name
ADD domain_constraint [ NOT VALID ]
ALTER DOMAIN name
DROP CONSTRAINT [ IF EXISTS ] constraint_name [ RESTRICT | CASCADE ]
ALTER DOMAIN name
RENAME CONSTRAINT constraint_name TO new_constraint_name
ALTER DOMAIN name
VALIDATE CONSTRAINT constraint_name
ALTER DOMAIN name
OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER DOMAIN name
RENAME TO new_name
ALTER DOMAIN name
SET SCHEMA new_schemaALTER 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 [ NOT VALID ]
This form adds a new constraint to a domain using the same syntax as CREATE 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 the NOT VALID option; the constraint can later be made valid using ALTER DOMAIN ... VALIDATE CONSTRAINT. Newly inserted or updated rows are always checked against all constraints, even those marked NOT VALID. NOT VALID is only accepted for CHECK constraints.
DROP CONSTRAINT [ IF EXISTS ]
This form drops constraints on a domain. If IF 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 as NOT VALID, that is, it verifies that all values in table columns of the domain type 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 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 domains schema. (These restrictions enforce that altering the owner doesnt do anything you couldnt do by dropping and recreating the domain. However, a superuser can alter ownership of any domain anyway.)
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 stored data for constraint validity.
CASCADE
Automatically drop objects that depend on the constraint, and in turn all objects that depend on those objects (see Section 5.14).
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.
Although ALTER DOMAIN ADD CONSTRAINT attempts to verify that existing stored data satisfies the new constraint, this check is not bulletproof, because the command cannot “see” table rows that are newly inserted or updated and not yet committed. If there is a hazard that concurrent operations might insert bad data, the way to proceed is to add the constraint using the NOT VALID option, commit that command, wait until all transactions started before that commit have finished, and then issue ALTER DOMAIN VALIDATE CONSTRAINT to search for data violating the constraint. This method is reliable because once the constraint is committed, all new transactions are guaranteed to enforce it against new values of the domain type.
Currently, ALTER DOMAIN ADD CONSTRAINT, ALTER DOMAIN VALIDATE CONSTRAINT, and ALTER DOMAIN SET NOT NULL will fail if the named domain or any derived domain is used within a container-type column (a composite, array, or range column) in any table in the database. They should eventually be improved to be able to verify the new constraint for such nested values.
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 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;
ALTER DOMAIN conforms to the SQL standard, except for the OWNER, RENAME, SET SCHEMA, and VALIDATE CONSTRAINT variants, which are PostgreSQL extensions. The NOT VALID clause of the ADD CONSTRAINT variant is also a PostgreSQL extension.
CREATE DOMAIN (CREATE_DOMAIN(7)), DROP DOMAIN (DROP_DOMAIN(7))