select a.c1,b.c2,d.c3,e.c4
from a
left join b
on a.id1 = b.id
left join c
on a.id2 = c.id2
left join d
on a.id3 = d.id3
left join e
on a.id = e.id
from a
left join b
on a.id1 = b.id
left join c
on a.id2 = c.id2
left join d
on a.id3 = d.id3
left join e
on a.id = e.id
A E
id num id num1
aa 1 aa 3
bb 2 bb 4
aa 5那么select a.id,a.num,b.num1 from a,b where a.id = b.id;出来的结果是:
aa 1 3
aa 5 3
bb 2 4就正确啊。怎么造成了重复数据?需要说清楚。
你想要什么样的结果,也要说明白。