Constraining Attribute Values

• Constrain invalid values

  • NOT NULL
  • gender CHAR(1)
    CHECK (gender IN (‘F’, ‘M’))
  • MovieName CHAR(30)
    CHECK (MovieName IN
    (SELECT MovieName FROM Movies))

• The constraint is checked whenever the value of the attribute is changed or added.

• Isn’t this the same as REFERENCE?

Next slide

Back to first slide

View graphic version