Defining Domain-based Columns

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When you create a table, you can set column attributes by using an existing domain definition that has been previously stored in the database. A domain is a global column definition. Domains must be created with the CREATE DOMAIN statement before you can reference them to define columns locally. For information on how to create a domain, see Working with Domains.

Domain-based columns inherit all the characteristics of a domain, but the column definition can include a new default value, additional CHECK constraints, or a collation clause that overrides the domain definition. It can also include additional column constraints. You can specify a NOT NULL setting if the domain does not already define one.

Note

You cannot override the domain’s NOT NULL setting with a local column definition.

For example, the following statement creates a table, COUNTRY, referencing the domain, COUNTRYNAME, which was previously defined with a data type of VARCHAR(15):

CREATE TABLE COUNTRY
(COUNTRY COUNTRYNAME NOT NULL PRIMARY KEY,
 CURRENCY VARCHAR(10) NOT NULL);