语句  SELECT DISTINCT CName  FROM SCInfo b JOIN stInfo a ON a.StID=b.StID      JOIN CInfo c ON b.CNo =c.CNo   WHERE StSex ='男'  EXCEPT  SELECT DISTINCT CName   FROM SCInfo b JOIN stInfo a ON a.StID=b.StID      JOIN CInfo c ON b.CNo =c.CNo  WHERE StSex ='女'和语句  SELECT DISTINCT CName   FROM SCInfo b JOIN stInfo a ON a.StID=b.StID      JOIN CInfo c ON b.CNo =c .CNo   WHERE StSex ='男' AND CName NOT IN (     SELECT DISTINCT CName      FROM SCInfo b JOIN stInfo a ON a.StID=b.StID         JOIN CInfo c ON b.CNo =c.CNo       WHERE StSex ='女' )功能完全一致。