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 [...]
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 [...]
Three Ways to Classify a Relationship
Some basic terminology applies to relationships. The entities that are related are called participants, and the number of participants in a relationship is its degree. The vast majority of relationships are binary, having two participants, but unary relationships (a relation that is related to itself) are also common, while ternary relationships (with three participants) are [...]
Understanding Database For Newbies
Database terminology is almost as slippery as the term “object-oriented programming.” The word “database” can be used to describe everything from a single set of data, such as a telephone list, to a complex set of tools, such as SQL Server, and a whole lot in between. This lack of precision isn’t a bad thing, [...]
Nothing Mysterious In Relational Database
So, what is this mythical creature called a relational database? Briefly, it’s a tool for storing and manipulating information efficiently and effectively—”efficiently and effectively” in the sense that data is protected from accidental loss or corruption, that it doesn’t use more resources (human or computer) than necessary, and that it can be retrieved in sensible [...]