sql

找出至少选修了2号学生选修过的全部课程的学生号

提示:不存在这样的课程y，学生2选修了y，而学生x没有选。

SELECT DISTINCT Sno

   FROM SC as SCX

   WHERE NOT EXISTS

      (SELECT *

       FROM SC as SCY

       WHERE SCY.Sno =‘2’AND NOT EXISTS

                               (SELECT *

                                  FROM SC SCZ

                          WHERE SCZ.Sno=SCX.Sno AND SCZ.Cno=SCY.Cno))