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  1. The notions of superkey, candidate key and primary key all apply to the relational model.

  2. For example, in Branch-scheme,
  3. The primary key for Customer-scheme is {cname}.

  4. More formally, if we say that a subset of is a superkey for , we are restricting consideration to relations in which no two distinct tuples have the same values on all attributes in . In other words,

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Last Update: Wed Sep 20 15:45:57 PDT 1995