Normal Forms Shortcuts for Gate Students

Normal Forms Shortcuts for Gate Students I am trying to give you the normal forms shortcuts for Gate students. To identify that a relation is in which normal form, the first step is to Find all the Candidate Keys of the relation.

First Normal Form (1NF) : 

It doesn’t have multivalued attributes.

RollNo	Name	Subject	Marks
00001	AAAAA	Maths,C++	????
Error in 3rd Column (multivalue), as we can’t assign marks for both subjects in one column.

Solution : 

RollNo	Name	Subject	Marks
00001	AAAAA	Maths	89
00001	AAAAA	C++	98

Second Normal Form (2NF) : 

Check right hand side  of FD A → B ,

1. If B is a fullynonkey, then A must be either fullynonkey OR fully key. (i.e. it should not be partial)
2. If right hand side B is a key or part of key, then its okay – no need to check.
3. If its Nonkey → Nonkey, its fine – no need to check. Just check (1) is sufficient.

Third Normal Form (3NF) :

Check right hand side of FD A → B,

1. If B is fullynonkey, then left hand side must be either superkey or part of superkey.
2. Nonkey → Nonkey is not allowed in 3NF
3. Key or part of Key → Nonkey is allowed

Boyce-Codd Normal Form (BCNF) :

Left hand side A → B must be a superkey, whatever is Right Hand Side.

Decomposition in All Normal Form Violation 

If A → B is violating normal form in R(ABCD), then decompose into

• R1 = AB
• R2 = BCD

Some Notes about Normal Forms – Useful for Gate Students

	1NF	2NF	3NF	BCNF
Redundancy	Hgh	<1NF	<2NF	0% if it doesn’t contain MVD, Otherwise, it may contain Redundancy
Lossless Join	Always	Always	Always	Always
Dependency Preserving	Always	Always	Always	Some relation may not possible to decompose in BCNF by preserving dependency

	4NF
0% redundancy	Yes
Lossless	Yes
Dependency Preserving	may or may not be
Problem may exist ??	Join Dependency

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