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'\" t
.\"     Title: ALTER DOMAIN
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 2026
.\"    Manual: PostgreSQL 16.12 Documentation
.\"    Source: PostgreSQL 16.12
.\"  Language: English
.\"
.TH "ALTER DOMAIN" "7" "2026" "PostgreSQL 16.12" "PostgreSQL 16.12 Documentation"
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.SH "NAME"
ALTER_DOMAIN \- change the definition of a domain
.SH "SYNOPSIS"
.sp
.nf
ALTER DOMAIN \fIname\fR
    { SET DEFAULT \fIexpression\fR | DROP DEFAULT }
ALTER DOMAIN \fIname\fR
    { SET | DROP } NOT NULL
ALTER DOMAIN \fIname\fR
    ADD \fIdomain_constraint\fR [ NOT VALID ]
ALTER DOMAIN \fIname\fR
    DROP CONSTRAINT [ IF EXISTS ] \fIconstraint_name\fR [ RESTRICT | CASCADE ]
ALTER DOMAIN \fIname\fR
     RENAME CONSTRAINT \fIconstraint_name\fR TO \fInew_constraint_name\fR
ALTER DOMAIN \fIname\fR
    VALIDATE CONSTRAINT \fIconstraint_name\fR
ALTER DOMAIN \fIname\fR
    OWNER TO { \fInew_owner\fR | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER DOMAIN \fIname\fR
    RENAME TO \fInew_name\fR
ALTER DOMAIN \fIname\fR
    SET SCHEMA \fInew_schema\fR

where \fIdomain_constraint\fR is:

[ CONSTRAINT \fIconstraint_name\fR ]
{ NOT NULL | CHECK (\fIexpression\fR) }
.fi
.SH "DESCRIPTION"
.PP
\fBALTER DOMAIN\fR
changes the definition of an existing domain\&. There are several sub\-forms:
.PP
SET/DROP DEFAULT
.RS 4
These forms set or remove the default value for a domain\&. Note that defaults only apply to subsequent
\fBINSERT\fR
commands; they do not affect rows already in a table using the domain\&.
.RE
.PP
SET/DROP NOT NULL
.RS 4
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\&.
.RE
.PP
ADD \fIdomain_constraint\fR [ NOT VALID ]
.RS 4
This form adds a new constraint to a 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
\fBALTER DOMAIN \&.\&.\&. VALIDATE CONSTRAINT\fR\&. Newly inserted or updated rows are always checked against all constraints, even those marked
NOT VALID\&.
NOT VALID
is only accepted for
CHECK
constraints\&.
.RE
.PP
DROP CONSTRAINT [ IF EXISTS ]
.RS 4
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\&.
.RE
.PP
RENAME CONSTRAINT
.RS 4
This form changes the name of a constraint on a domain\&.
.RE
.PP
VALIDATE CONSTRAINT
.RS 4
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\&.
.RE
.PP
OWNER
.RS 4
This form changes the owner of the domain to the specified user\&.
.RE
.PP
RENAME
.RS 4
This form changes the name of the domain\&.
.RE
.PP
SET SCHEMA
.RS 4
This form changes the schema of the domain\&. Any constraints associated with the domain are moved into the new schema as well\&.
.RE
.PP
You must own the domain to use
\fBALTER DOMAIN\fR\&. To change the schema of a domain, you must also have
CREATE
privilege on the new schema\&. To alter the owner, you must be able to
SET ROLE
to the new owning role, and that role must have
CREATE
privilege on the domain\*(Aqs schema\&. (These restrictions enforce that altering the owner doesn\*(Aqt do anything you couldn\*(Aqt do by dropping and recreating the domain\&. However, a superuser can alter ownership of any domain anyway\&.)
.SH "PARAMETERS"
.PP
.PP
\fIname\fR
.RS 4
The name (possibly schema\-qualified) of an existing domain to alter\&.
.RE
.PP
\fIdomain_constraint\fR
.RS 4
New domain constraint for the domain\&.
.RE
.PP
\fIconstraint_name\fR
.RS 4
Name of an existing constraint to drop or rename\&.
.RE
.PP
NOT VALID
.RS 4
Do not verify existing stored data for constraint validity\&.
.RE
.PP
CASCADE
.RS 4
Automatically drop objects that depend on the constraint, and in turn all objects that depend on those objects (see
Section\ \&5.14)\&.
.RE
.PP
RESTRICT
.RS 4
Refuse to drop the constraint if there are any dependent objects\&. This is the default behavior\&.
.RE
.PP
\fInew_name\fR
.RS 4
The new name for the domain\&.
.RE
.PP
\fInew_constraint_name\fR
.RS 4
The new name for the constraint\&.
.RE
.PP
\fInew_owner\fR
.RS 4
The user name of the new owner of the domain\&.
.RE
.PP
\fInew_schema\fR
.RS 4
The new schema for the domain\&.
.RE
.SH "NOTES"
.PP
Although
\fBALTER DOMAIN ADD CONSTRAINT\fR
attempts to verify that existing stored data satisfies the new constraint, this check is not bulletproof, because the command cannot
\(lqsee\(rq
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
\fBALTER DOMAIN VALIDATE CONSTRAINT\fR
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\&.
.PP
Currently,
\fBALTER DOMAIN ADD CONSTRAINT\fR,
\fBALTER DOMAIN VALIDATE CONSTRAINT\fR, and
\fBALTER DOMAIN SET NOT NULL\fR
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\&.
.SH "EXAMPLES"
.PP
To add a
NOT NULL
constraint to a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode SET NOT NULL;
.fi
.if n \{\
.RE
.\}
.sp
To remove a
NOT NULL
constraint from a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode DROP NOT NULL;
.fi
.if n \{\
.RE
.\}
.PP
To add a check constraint to a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode ADD CONSTRAINT zipchk CHECK (char_length(VALUE) = 5);
.fi
.if n \{\
.RE
.\}
.PP
To remove a check constraint from a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode DROP CONSTRAINT zipchk;
.fi
.if n \{\
.RE
.\}
.PP
To rename a check constraint on a domain:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode RENAME CONSTRAINT zipchk TO zip_check;
.fi
.if n \{\
.RE
.\}
.PP
To move the domain into a different schema:
.sp
.if n \{\
.RS 4
.\}
.nf
ALTER DOMAIN zipcode SET SCHEMA customers;
.fi
.if n \{\
.RE
.\}
.SH "COMPATIBILITY"
.PP
\fBALTER DOMAIN\fR
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\&.
.SH "SEE ALSO"
CREATE DOMAIN (\fBCREATE_DOMAIN\fR(7)), DROP DOMAIN (\fBDROP_DOMAIN\fR(7))
F1l3 Manager
