表A
Aid Bid Aname 1 2 XX
2 1 XX
3 3 XX
4 4 XX
表B
Bid Bname Cid
1 YY 1
2 YY 3
3 YY 2
4 YY 4
表C
Cid Cname 1 ZZ
2 ZZ
3 ZZ
4 ZZ我要查出:
Aid Aname Bname Cname
Aid Bid Aname 1 2 XX
2 1 XX
3 3 XX
4 4 XX
表B
Bid Bname Cid
1 YY 1
2 YY 3
3 YY 2
4 YY 4
表C
Cid Cname 1 ZZ
2 ZZ
3 ZZ
4 ZZ我要查出:
Aid Aname Bname Cname
from A
left join B on A.Bid=B.Bid
left join C on B.Cid=C.Cid
a.aid,a.aname,b.bname,c.cname
from
a join b
on
a.bid=b.bid
join c on
b.cid=c.cid
select
Aid ,
Aname ,
Bname ,
Cname
from A
left join B on A.Bid=B.Bid
left join C on B.Cid=C.Cid
子查询慢
select a.aid,
a.name,
(select b.bname from b where b.bid = a.bid) bname,
(select c.cname from b , c where c.cid = b.cid and b.bid = a.bid) cname
from a