Candidate key known as minimal superkey - Database

Q.  Which of the following is / are known as a minimal superkey?
- Published on 26 Aug 15

a. Primary key
b. Foreign key
c. Unique key
d. Candidate key

ANSWER: Candidate key


  • Nirja Shah   -Posted on 02 Nov 15
    Candidate Key
    - This key can be any column or a combination of columns that can qualify as unique key in database.
    - There can be multiple Candidate Keys in one table.
    - Each Candidate Key can qualify as Primary Key.

    Primary Key
    - This key is a column or a combination of columns that uniquely identify a record. Only one Candidate Key can be Primary Key.

    Unique Key
    - This key is a set of zero, one, or more attributes.
    - The value(s) of these attributes are required to be unique for each tuple (row) in a relation.
    - The value, or combination of values, of unique key attributes for any tuple should not be repeated for any other tuple in that relation.

    Foreign Key
    - This key is a field (or collection of fields) in one table that uniquely identifies a row of another table.
    - In simpler words, the foreign key is defined in a second table, but it refers to the primary key in the first table.

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