Sunday, March 16, 2014

Strong Entity Set

 Strong Entity Set to Relation Schema

A strong entity set is an entity set that has one or more attributes as a key to uniquely identify each entity.

A Strong Entity Set can be converted into Relations Schema using the following rule;

  • Convert a strong entity set into relation schema with all the simple attributes as columns of the relation schema and name of the entity set as name of the relation schema.

Consider the entity sets Department and Employee in Figure 1. Both are Strong as they have primary keys (DNo for Department, EID from Employee). Let us convert the Department table into relation schema as follows;
Department (DNo, DName, DLocation)

Not all the attributes are simple for Employee, so, we shall discuss it later.


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