Data integrity constraint classification
Before we start investigating the complexities involved in implementing data integrity constraints using database triggers, we will first introduce a classification schema for data integrity constraints. Agreeing upon a classification scheme for constraints, helps us a lot in implementing them: for we can then approach the problem area on a class-by-class basis. A classification scheme needs to have a few properties: 1. The constraint classes should be mutually exclusive : any given constraint should clearly fall into one, and only one, of the classes; 2. The scheme should cover all types of constraints : i.e. it cannot be that we can think of a constraint that doesn't fall into one of the defined classes; 3. It should be practical : and by this we mean it should help us when implementing constraints. Or, put in another way, the issues we have when implementing constraints of the ...