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.

2nf shortcut - Normal Forms Shortcuts for Gate Students

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

3nf shortcut - Normal Forms Shortcuts for Gate Students

Boyce-Codd Normal Form (BCNF) :

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

BCNF shortcut - Normal Forms Shortcuts for Gate Students

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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Join Dependencies and Fifth Normal Form (5NF) Questions on Identify the Normal Forms of relation R

     

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