Provided by: postgresql-client-8.0_8.0.7-2build1_i386 bug

NAME

       CREATE DOMAIN - define a new domain

SYNOPSIS

       CREATE DOMAIN name [AS] data_type
           [ DEFAULT expression ]
           [ constraint [ ... ] ]

       where constraint is:

       [ CONSTRAINT constraint_name ]
       { NOT NULL | NULL | CHECK (expression) }

DESCRIPTION

       CREATE  DOMAIN creates a new data domain. The user who defines a domain
       becomes its owner.

       If a schema name is given (for example, CREATE DOMAIN myschema.mydomain
       ...)  then  the domain is created in the specified schema. Otherwise it
       is created in the current schema.  The domain name must be unique among
       the types and domains existing in its schema.

       Domains  are useful for abstracting common fields between tables into a
       single location for maintenance. For example, an email  address  column
       may  be  used in several tables, all with the same properties. Define a
       domain and use that rather than setting  up  each  table’s  constraints
       individually.

PARAMETERS

       name   The  name  (optionally  schema-qualified)  of  a  domain  to  be
              created.

       data_type
              The underlying data type of the domain. This may  include  array
              specifiers.

       DEFAULT expression
              The  DEFAULT clause specifies a default value for columns of the
              domain data type. The value is any variable-free expression (but
              subqueries  are  not  allowed).   The  data  type of the default
              expression must match the data type of the domain. If no default
              value is specified, then the default value is the null value.

              The default expression will be used in any insert operation that
              does not specify a value for the column. If a default  value  is
              defined  for  a  particular  column,  it  overrides  any default
              associated  with  the  domain.  In  turn,  the  domain   default
              overrides  any default value associated with the underlying data
              type.

       CONSTRAINT constraint_name
              An optional name for a constraint. If not specified, the  system
              generates a name.

       NOT NULL
              Values of this domain are not allowed to be null.

       NULL   Values  of  this  domain  are  allowed  to  be null. This is the
              default.

              This clause is only intended for compatibility with  nonstandard
              SQL databases. Its use is discouraged in new applications.

       CHECK (expression)
              CHECK  clauses  specify  integrity  constraints  or  tests which
              values of the domain must satisfy.  Each constraint must  be  an
              expression  producing  a  Boolean result. It should use the name
              VALUE to refer to the value being tested.

              Currently, CHECK expressions cannot contain subqueries nor refer
              to variables other than VALUE.

EXAMPLES

       This  example  creates  the  us_postal_code data type and then uses the
       type in a table definition. A regular expression test is used to verify
       that the value looks like a valid US postal code.

       CREATE DOMAIN us_postal_code AS TEXT
       CHECK(
          VALUE ~ ’^\d{5}$’
       OR VALUE ~ ’^\d{5}-\d{4}$’
       );

       CREATE TABLE us_snail_addy (
         address_id SERIAL NOT NULL PRIMARY KEY
       , street1 TEXT NOT NULL
       , street2 TEXT
       , street3 TEXT
       , city TEXT NOT NULL
       , postal us_postal_code NOT NULL
       );

COMPATIBILITY

       The command CREATE DOMAIN conforms to the SQL standard.

SEE ALSO

       ALTER DOMAIN [alter_domain(7)], DROP DOMAIN [drop_domain(l)]