Welcome to WebmasterServe!

FREE TO JOIN! Join us now to engage in informative and friendly discussions about Webmastering, SEO, SEM, Internet Marketing, Programming, Graphic Design, Online Jobs and more. What are you waiting for? Ready to join our friendly community? It takes just one minute to register.

Dismiss Notice

Join WebmasterServe Forums 
Join the discussion! Have a better idea or an opinion? It takes just one minute to register Click Here to Join

Help Me/Question What Is Candidate Key, Super Key And Secondary Key?

Discussion in 'Database Management' started by krishatg, Mar 16, 2016.

  1. krishatg

    Yellow Belt

    Joined:
    Jan 16, 2016
    Messages:
    240
    Ratings:
    +14 / -0
    • Candidate Key : it ensures uniqueness and irreduceability i.e no proper subset of A has the uniqueness property.There could be multiple candidate keys however among those only 1 is choosen as primary key and other becomes alternat3 keys. No null value is allowed in candidate key column.
    • Super Key: A super key has uniqueness property and may or may not be irreduceable i.e a proper subset of A could have the uniqueness property.
    • Sencondary key: it is an attribute or combination of attributes that may not be a candidate key but classify the entity set on the particular characteristics.
     
  2. Swati Mishra

    Yellow Belt

    Joined:
    Dec 28, 2015
    Messages:
    644
    Ratings:
    +105 / -0
    A candidate key is subset of super key.A candidate key is single field or the least combination of fields that uniquely identifies each record in table.

    and the super key is the combination of attributes.
     

Share This Page