Any time two columns of the table need to be specified in the constraint, a table-level check constraint is required. In addition to check constraints Microsoft provides rules. Rules are free-standing database objects that can be used to enforce data integrity. This is desirable because it promotes reusability . Check constraints always must be defined within the scope of a table.
Rules define the parameters for data validation.
Once bound, similar to a check constraint, whenever data is inserted or updated, the rule is checked to ensure that the data modification complies with the rule. Both columns and user-defined data types can have rules defined for them. Rules are created using the create rule DDL statement. The edit picture shows that the valid values for a grade can be the letters A through F with a space, a plus sign, or a minus sign appended to the letter. After the rule has been created, it can be bound to columns and user-defined data types.