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Question number: 238

» Database » Oracle

Essay Question▾

Describe in Detail

What is join dependency and inclusion dependency?

Explanation

Join Dependency:

  • When we decompose table those decomposed table should satisfy join dependency.

  • Dependency is generalization of multivalued dependency.

  • A is said to hold over a relation R if is a lossless-join decomposition of R.

  • No set of sound and complete inference rules exist for JD.

  • Important in connection with the decomposition technique for schema design and normalization.

  • Decomposition technique avoids redundancies due to data dependencies by decomposing a relation into smaller parts.

Example:

Understanding example of join dependency(JD).

Understanding Example of Join Dependency (JD).

Understanding example of join dependency (JD).

Inclusion Dependency:

Define Inclusion Dependencies.

Define Inclusion Dependencies.

Define Inclusion Dependencies.

  • A statement of the form that some columns of a relation are contained in other columns.

  • A foreign key constraint is an example of inclusion dependency.

  • Defined in order to formalize two types of inter relational constraints:

    • The foreign key constraint cannot be specified as a functional or multi valued dependency because it relates attributes across relations.

    • Constraint between two relations that represent a class or a subclass relationship also it has no formal definition in terms of the functional, multi valued, and join dependencies.

Example of Inclusion dependencies:

Example of Inclusion dependencies

Example of Inclusion Dependencies

Example of Inclusion dependencies