The SQL operations union, intersect, and except operate on relations and correspond to the mathematical set-theory operations ∪, ∩, and −. We shall now construct queries involving the union, intersect, and except operations over two sets.
• The set of all courses taught in the Fall 2009 semester:
where semester = ’Fall’ and year= 2009;
• The set of all courses taught in the Spring 2010 semester:
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