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.
|Error in 3rd Column (multivalue), as we can’t assign marks for both subjects in one column.|
Second Normal Form (2NF) :
Check right hand side of FD A → B ,
- If B is a fullynonkey, then A must be either fullynonkey OR fully key. (i.e. it should not be partial)
- If right hand side B is a key or part of key, then its okay – no need to check.
- 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,
- If B is fullynonkey, then left hand side must be either superkey or part of superkey.
- Nonkey → Nonkey is not allowed in 3NF
- 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
|Redundancy||Hgh||<1NF||<2NF||0% if it doesn’t contain MVD, Otherwise, it may contain Redundancy|
|Dependency Preserving||Always||Always||Always||Some relation may not possible to decompose in BCNF by preserving dependency|
|Dependency Preserving||may or may not be|
|Problem may exist ??||Join Dependency|
|Join Dependencies and Fifth Normal Form (5NF)||Questions on Identify the Normal Forms of relation R|