按你的写法直接关联就可以了啊SELECT x.Sno,x.Cno,x.Grade,z.CnameFROM SC x,Course zWHERE x.Cno=z.Cno andx.Grade>=(SELECT AVG(Grade)FROM SC yWHERE y.Sno=x.Sno)ORDER BY x.Sno ,x.cno