Named Constraints

A constraint can be named explicitly if the CONSTRAINT clause is used for its definition.By default, the constraint index will have the same name as the constraint.If a different name is wanted for the constraint index, a USING clause can be included.

The USING clause allows you to specify a user-defined name for the index that is created automatically and, optionally, to define the direction of the index — either ascending (the default) or descending.