mysql左连接与oracle(+)使用对比
由于mysql不能像oracle一样使用(+)做外连接，使用left join或者right join需要注意

oracle： select a.aid aid , b.bid bid ,c.cid cid , d.did did , e.eid eid from tablea a , tableb b ,tablec c ,tabled d ,tablee e wherea.aid = b.aid (+)and a.aid = c.aid(+)and b.bid = d.bid (+)and d.did = e.eid (+)order by a.aid , b.bid , c.cid , d.did ,e.eid;mysql：select a.aid aid , b.bid bid ,c.cid cid , d.did did , e.eid eid from tablea a left join         (        tableb b left join                 (                         tabled d left join tablee e                         on (d.did = e.eid)                 )                on (b.bid = d.bid )          )        on ( a.aid = b.aid)        left join tablec c         on a.aid = c.aidorder by a.aid , b.bid , c.cid , d.did ,e.eid;

引至http://www.itpub.net/thread-1122562-1-1.html