Use Of Domains In Declarations

A domain name can be specified as the type of a PSQL parameter or local variable.The parameter or variable will inherit all domain attributes.If a default value is specified for the parameter or variable, it overrides the default value specified in the domain definition.

If the TYPE OF clause is added before the domain name, only the data type of the domain is used: any of the other attributes of the domain — NOT NULL constraint, CHECK constraints, default value — are neither checked nor used.However, if the domain is of a text type, its character set and collation are always used.

Input and output parameters or local variables can also be declared using the data type of columns in existing tables and views.The TYPE OF COLUMN clause is used for that, specifying relationname.columnname as its argument.

When TYPE OF COLUMN is used, the parameter or variable inherits only the data type and — for string types — the character set and collation.The constraints and default value of the column are ignored.