DELETE FROM SC
WHERE Cno in(
SELECT SC.Cno FROM Student,SC
WHERE Sdept='计算机' AND Grade<60 AND Student.Sno=SC.Sno)
单独执行一下子查询这条语句,看看有没有符合条件的记录
SELECT SC.Cno FROM Student,SC
WHERE Sdept='计算机' AND Grade<60 AND Student.Sno=SC.Sno
有可能你select函数没有数据
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