sql关联有关问题ABC三个表

sql关联问题A\B\C三个表，
sql关联问题A\B\C三个表，A.id = B.aid 和A.id= C.a2id，这种关联如何写？
------解决思路----------------------

select A.*,B.*,C.* from A
left join B on A.id = B.aid
left join C on A.id = B. a2id

------解决思路----------------------
$user = M('A');
$user->join("left join B on A.id=B.Id left join C on c.id=b.id")->field("A.id as aid,B,id as bid,……")->select();