Implementing Data Integrity
In this blog post, we’ll look at a few of the issues involved in creating the physical model of the problem space: the database schema. Moving from one level to another is primarily a change in terminology—relations become tables and attributes become fields—except for issues of data integrity. These never map quite as cleanly as [...]
What is Database Integrity
Database Integrity The most general form of integrity constraint is the database constraint. Database constraints reference more than one relation: “A Customer is not allowed to have a status of ‘Preferred’ unless he or she has made a purchase in the last 12 months.” The majority of database constraints take this form. It’s always a [...]
Transition Integrity in Relational Database
You would use transitional integrity constraints, for instance, to ensure that the status of a given order never changed from “Entered” to “Completed” without passing through the interim states, or to prevent a canceled order from changing status at all. The status of an entity is usually controlled by a single attribute. In this case, [...]
Domain Integrity in Relational Database
A domain is the set of all possible values for a given attribute. A domain integrity constraint—usually just called a domain constraint—is a rule that defines these legal values. It might, of course, be necessary to define more than one domain constraint to describe a domain completely. A domain isn’t the same thing as a [...]
Functional Dependency in Relational Database
Functional Dependency in Relational Database The concept of functional dependency is an extremely useful tool for thinking about data structures. Given any tuple T, with two sets of attributes {X1…Xn} and {Y1…Yn} (the sets need not be mutually exclusive), then set Y is functionally dependent on set X if, for any legal value of X, [...]