Constraining Values with User Defined ‘Types’

• Can define new domains to use as the attribute type...

  CREATE DOMAIN GenderDomain CHAR(1)
  
  CHECK (VALUE IN (‘F’, ‘M’));

• Then update our attribute definition...

  gender GenderDomain
  

• Note use of VALUE to refer to the attribute value.

• Deferred constraints: deal with circular referencial integrity constraints.

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