update bb set num=(select sum(dd.num2) from aa,bb,cc,dd
where aa.aid=bb.aid
and bb.cid=cc.cid and cc.cid=dd.cid
and aa.id1=1 and cc.flag=1
group by dd.cid)
where bb.aid=(select aa.aid from aa,bb,cc,dd
where bb.cid=cc.cid and cc.cid=dd.cid
and aa.id1=1 and cc.flag=1)
where aa.aid=bb.aid
and bb.cid=cc.cid and cc.cid=dd.cid
and aa.id1=1 and cc.flag=1
group by dd.cid)
where bb.aid=(select aa.aid from aa,bb,cc,dd
where bb.cid=cc.cid and cc.cid=dd.cid
and aa.id1=1 and cc.flag=1)
这样