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select a.aid,b.bid,count(c.cid) cnt
from a
inner join b on
b.aid=a.aid
inner join c on
c.bid=b.bid
group by
a.aid,b.bid
A:
AID,Title (题号ID,题内容)
B:
BID,AID,Title (选项ID,题号ID,选项描述)
C:
CID,AID,BID (回答ID,题ID,选项ID)
要取得C表中选择各题的数量,用如下SQL即可解决:
SELECT a.AID,b.Bid,Count(C.CID) Num FROM C c WHERE c.AID in(SELECT B.AID FROM B b, C c WHERE a.AID=b.AID)
select (select a.Title from A a where a.AID=b.BID) as question,b.Title as answer,(select sum(c.CID) from C c where c.BID=b.BID) as count
from B b