Lecture on First Normal Form (1NF)
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First Normal Form (1NF):
The following criterias must be satisfied for 1NF.

  1. Values of each attribute is atomic.
  2. No composite values
  3. All entries in any column must be of the same kind
  4. Each column must have a unique name
  5. No two rows are identical  

Consider the below Student table

Roll Name Courses
101 Asif DBMS, CN, CD, SE
102 Amit CO, OS
103 Arpit CD, OS, CN, DBMS

Here you can see that column Courses contain multiple values in a single rows. This is not allowed in 1NF.
We can convert this table into 1NF as below,

Roll Name Courses
101 Asif DBMS
101 Asif CN
101 Asif CD
101 Asif SE
102 Amit CO
102 Amit OS
103 Arpit CD
103 Arpit OS
103 Arpit CN
103 Arpit DBMS

 

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3Comments
Manu F Gomez @manufg 28 Jan 2017 11:49 am

Sir, how is BC a candidate key?. candidate key means a minimal super key right. A is a candidate key, as it is a superkey and has minimal set of attributes. So how BC becomes candidate key as it does not have minimal set of attributes.?

Sumit Verma @sumitverma 14 Apr 2017 12:55 pm

@manufg
Candidate key is the minimal key not a key with minimum attributes.
Here A is candidate key, so any superset of attribute A will be superkey not a candidate key. 
BC is not a superset of A and if we can get all the attributes from BC then yes, BC will be candidate key.
 

shweta @shweta1920 30 Apr 2017 04:28 pm

sir after resolving the first relation ... in 2nd relation which will be the primary key???