Description
CREATE DOMAIN allows the user to register a new data domain with
PostgreSQL for use in the current data base. 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 one at the front of the search path; see 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. 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.
Examples
This example creates the country_code data type and then uses the
type in a table definition:
CREATE DOMAIN country_code char(2) NOT NULL;
CREATE TABLE countrylist (id INT4, country country_code);
