select aid, b.bname as firstb, b2.bname as secondb, b3.bname as thirdb
from a left join b
on a.aid = b.aid
and b.level = 1
left join b1
on a.aid = b1.aid
and b1.level = 2
left join b2
on a.aid = b2.aid
and b2.level = 3
from a left join b
on a.aid = b.aid
and b.level = 1
left join b1
on a.aid = b1.aid
and b1.level = 2
left join b2
on a.aid = b2.aid
and b2.level = 3
解决方案 »
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