Candidate key known as minimal superkey - Database

Discussion

• 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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