Referential Integrity in Relational Database
In this blog post, let’s at the decomposition of relations to minimize redundancy and at foreign keys to implement the links between relations. If these links are ever broken, the system will be unreliable at best and unusable at worst. Referential integrity constraints maintain and protect these links. There is really only one referential integrity [...]
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 [...]
Entity Relationship Model
The Entity Relationship model, which describes data in terms of entities, attributes, and relations, was introduced by Peter Pin Shan Chen in 1976.2 At the same time, he proposed a method of diagramming called Entity Relationship (E/R) diagrams, which has become widely accepted. E/R diagrams use rectangles to describe entities, ellipses for attributes, and diamonds [...]
Relational Model in Database Based on Mathematics
The relational model is based on a collection of mathematical principles drawn primarily from set theory and predicate logic. These principles were first applied to the field of data modeling in the late 1960s by Dr. E. F. Codd, then a researcher at IBM, and first published in 1970. The relational model defines the way [...]