Multivalued dependency and join dependency can be used to guide database design although they both are less common than functional dependencies.
Inclusion dependencies are quite common. They typically show little influence on designing of the database.
The inclusion dependency is a statement in which some columns of a relation are contained in other columns.
The example of inclusion dependency is a foreign key. In one relation, the referring relation is contained in the primary key column(s) of the referenced relation.
Suppose we have two relations R and S which was obtained by translating two entity sets such that every R entity is also an S entity.
Inclusion dependency would be happen if projecting R on its key attributes yields a relation that is contained in the relation obtained by projecting S on its key attributes.
In inclusion dependency, we should not split groups of attributes that participate in an inclusion dependency.
In practice, most inclusion dependencies are key-based that is involved only keys.
0 Comments