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DBMS

DBMS Key Super | CrackEase

Super Key in DBMS

Super Key

A super key is a set of one or more attributes (columns) that, taken together, can uniquely identify every record (row) in a table.

Super keys may include extra attributes that are not necessary for uniqueness — in other words, a super key can be non-minimal.

Example of the super key
IDNAMEPHONEAGE
66John783297347723
67Judy973286746421
68Elena892382647625
69John732624784423

Possible Super Keys

  • [ID] — Since ID is unique for every person, it qualifies as a super key.
  • [NAME, ID] — Combination is also a super key; it contains the minimal identifying attribute (ID) plus an extra attribute (NAME).
  • [PHONE] — Phone uniquely identifies a person here, so PHONE is a super key as well.

Note: every candidate key is a super key, but not every super key is a candidate key. Candidate keys are minimal super keys (no unnecessary attributes).

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