两个思路。

一个是拆分join 然后在应用端join

二个是看能否延迟关联，比如
select * from a
inner join b on a.id = b.id
left join c on b.id = c.id
where a.id = 1 and b.field =xx

可以改为 a,b表where条件都很小了。
那就改为
select * from
(
select a.xx,b.xx from a inner join b on a.id = b.id
where a.id = 1 and b.field =xx
) as t
left join c on t.id = c.id