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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

    Jan 16, 2016
    +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

    Dec 28, 2015
    +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.

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