Frequently Asked Questions on Join Dependency

Why join dependencies are used?

Join dependencies are used to maintain the data consistency, data integrity, and efficiency in the database. Join dependency provides consistency across all the tables present in the databases.

Which normal form is related to the join dependencies?

5th Normal Form (5NF) is related to the join dependency which is also known as Project-join Normal form.

What is the difference between Multi-valued dependency and Join Dependency?

When the dependency is related to 2 sets of values only then it is called an MVD(muti-valued dependency). But if the number of sets of values gets increased then it is called a Join dependency. Multi-valued dependencies are used in 4NF whereas Join dependency is related to 5NF.

Are the join dependencies used in the industry?

Due to complexity and cost created due to join dependency, it is less frequently used in indusrty for normalization purpose.

Join Dependency means re-creating the original Table by joining multiple sub-tables of the given Table. It is a further generalization of MVD(multi-valued Dependencies).

• When a relation R can be obtained by joining the R1, R2, R3…, Rn where R1, R2, R3…, Rn are sub-relations of R, it is called a Join Dependency.
• R1,R2,R3…Rn are the sub-relations composed or derived from the relation R.