Inclusion Dependency

  • 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.

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Inclusion Dependence