Creates a constraint for the named domain. Specify a domain constraint when you create a domain to limit which values can be stored in columns based on the domain. Domain constraints specify that columns based on the domain contain only certain data values or that data values can or cannot be null. Use the CHECK clause to specify that a value must be within a specified range or that it matches a list of values. When you specify a CHECK clause for a domain constraint, you ensure that all values stored in columns based on the domain are checked consistently.