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Super key - RDBMS Primary key - RDBMS
Candidate key - RDBMS - SQL
72    Arnab De    21/11/2021   

All the minimal super key with no redundant attributes is known as candidate key.

Lets consider, a relation called Emp

Emp
Emp_SSN Emp_No Emp_Name
1234544434 E-001 Pradipta Pal
5345232444 E-002 Abhijit Ganguly
4645673422 E-003 Suman Banerjee
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In the above relation only two set of attribute can declarred as candidate key out of the six super keys, because other four keys have redundant attributes that are not necessary for unique identification

  • {Emp_SSN}
  • {Emp_Number}

Therefore, these two sets of attributes are candidate keys among the all other sets.

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Note
All the candidate keys are super keys, but not vice versa. Because candidate keys are the sub set of super keys.

Super key - RDBMS Primary key - RDBMS
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Author Details
Arnab De
I have over 16 years of experience working as an IT professional, ranging from teaching at my own institute to being a computer faculty at different leading institute across Kolkata. I also work as a web developer and designer, having worked for renowned companies and brand. Through tutorialathome, I wish to share my years of knowledge with the readers.
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