This exercise is worth a total of 15 points. You will receive up to five points for each correctly described constraint matching the business rules outlined below, and up to an additional five points for a correctly described business rule matching the constraint outlined below.
- Background:
In the preceding lesson, you learned that many (not all) business rules can be imposed on the logical schema by the database designer, who places constraints on table fields and relationships between tables to force business rules to be honored.
These constraints are then enforced by the RDBMS. By examining the existing database(s), you may be able to “spot” constraints already in place and work backwards to the business rule from which it was derived. But, more commonly, you are apprised of business rules, and must create the constraints yourself.
- Instructions:
Below are two business rules and one constraint. For each business rule, compose a single sentence that generally describes the constraint you would impose. (A sentence might read something like this: Place a (relationship or field) constraint on ….)
For the constraint, compose a single sentence that posits the probable business rule.
- Business rule: No single customer order may be less than $1.00 or exceed $500.00.
- Business rule: No high-school instructor can sponsor more than two student committees.
- Constraint: Only MasterCard, VISA, and Discover button options appear on an order form.