First three normal forms are important from exam point of view; we will discuss other normal forms viz. BCNF, 4NF and 5NF for sake of completeness. If you are not familiar about concept of normalization, do go through them first:
Boyce-Codd normal form (BCNF) named after its creators is based on the concept of determinant.
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We know that if B is functionally dependent on A, that is, A functionally determines B then in such case A is called determinant.
A table is in BCNF form if the only determinants in the table are the candidate keys. It means every column, on which some other column is fully functionally dependent, is also a candidate for the primary key of the table.
A table is in the fourth normal form (4NF) if:
Let’s say we have table Teacher which gives information about:
We can see that Narendra is teaching three subjects and knows two languages, thus there are two independent multi-valued dependencies. We can split the table into two tables.
You can see know that there is less data redundancy.
A table is in the fifth normal form (5NF), if:
This normal form is theoretical in nature, so we will not discuss it further. That concluded the discussion of normalization.
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Read next: SQL – Structured Query Language ››
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