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Sunday, March 20, 2016

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What is Entity-Set and Keys in DBMS?

Leke Oyetoke - Sunday, March 20, 2016


What is Entity-Set and Keys?

Key is defined as an attribute or set of attributes that uniquely points out an entity among entity set.

For instance, the roll_number of a student makes him/her identifiable among students.

1. Super Key: It is a set of attributes one or more that cooperatively distinguishes an entity in an entity set.

2. Candidate Key: This is a minimal super key. An entity set may contain more than one candidate key.

3. Primary Key: Primary key is one of the candidate keys selected by the database designer to uniquely and distinctively identify or point out the entity set.


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