Normalization is an important topic to crack Gate . Experts at GATE – prepladder  shares  5 quick tips to solve questions on normalization.

 

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For analyzing relations based on their primary key and functional dependencies, Normailization is used. Normalization is often performed as a series of tests on a relation to determine whether it satisfies or violates the requirements of a given normal form.

5 quick Tips to solve Questions on Normalization

#Tip1

1NF =>entry should have at most 1 single value, no repeating group,no 2 rows should be same

#Tip2

 2NF => it is related with partial dependencies. A relation is in 2 NF when every non-key attributes are dependent on the candidate key

#Tip3

3NF =>  now this talks about transitive dependencies. It exists when  A-->B-->C  and not  A-->C.In 3NF there should no A->C if A->B and B->C.

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#Tip4

Boyce-Codd Normal Form (BCNF) => checks about determinant. Left side of determined is called determinant. It makes sure all determinants are candidate keys.

#Tip5

4NF => Deals with multi-valued dependencies , X ->> Y means for each value of X, we can have more than one value of Y. It prevents nontrival MVD’s. For 5NF , A relation is in 5 NF if further cannot be non-loss decomposed

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Here is process of normalization.

 


 

Solved Examples From GATE

 

Q1.         Consider the following implications relating to functional and multivalued dependencies given below, which may or may not be correct.

  1. If A ->> B and A ->> C, then A -> BC
  2. If A ->   B and A ->  C then A ->> BC
  3. If A ->> BC and A -> B and A ->C
  4. If A -> BC and A ->  B   and A ->> C

Exactly how many of the above implications are valid?

A) 0 (B)  1            (C)  2         (D)  3 

Soln.      Answer is C

                In DBMS, we can see that

                If A   ->->  B and  A->-> C  then A -> BC

                And A ->-> BC then     A  ->-> BC

Hence, answer is (c)

 

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Q2.         Examine the table shown below.

               

branchNo

branchAddress

telNos

B001

8 Jefferson Way, Portland, OR 97201

503-555-3618, 503-555-6534

B002

City Centre Plaza, Seattle, WA 98122

206-555- 6756, 206-555 -8836

B003

14 – 8th Avenue, New York, NY 10012

212 -371 – 3000

B004

16 – 14th Avenue, Seattle, WA 98128

206 – 555 – 3131, 206 – 555 – 4112

 

  • Why is this table not in I NF?
  • Describe and illustrate the process of normalizing the data shown in this table to third normal form (3NF)

Soln.             

      

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