Can you Explain Fourth Normal Form?

 Posted by ArticlesMaint on 9/18/2009 | Category: Sql Server Interview questions | Views: 6629

Note: - Whenever the interviewer is trying to go above the third normal form, there can be two reasons, ego or to fail you. Three normal forms are really enough, practically anything more than that is an overdose.

In fourth normal form, it should not contain two or more independent multi-valued facts about an entity and it should satisfy “Third Normal form”.

So let us try to see what multi-valued facts are. If there are two or more many-to-many relationship in one entity and they tend to come to one place, it is termed as “multi-valued facts”.

Multi-valued facts

In the above table, you can see that there are two many-to-many relationships between Supplier / Product and “Supplier / Location (or in short multi-valued facts). In order for the above example to satisfy the fourth normal form, both the many-to-many relationships should go in different tables.

Normalized to Fourth Normal form.

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