update student a set weight_avg =
( select sum(b.cj*c.weight)/sum(c.weight)
from chengji b, kecheng c
where a.sno=b.sno and b.cno=c.cno
group by b.sno
);
( select sum(b.cj*c.weight)/sum(c.weight)
from chengji b, kecheng c
where a.sno=b.sno and b.cno=c.cno
group by b.sno
);
解决方案 »
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