一个事实表和多个维表表leftjoin怎么建索引比如事实表a表（500W数据）和维表a1,a2,a3,a4,a5左关联leftjoin,维表a1,a2,a3,a4,a5和事实表a关联的字段都建了索引,事实表a表与维表a1,a2,a3,a4,a5关联的字段

Question

一个事实表和多个维表表left join怎么建索引
比如事实表a表（500W数据）和维表a1,a2,a3,a4,a5左关联left join,维表a1,a2,a3,a4,a5和事实表a关联的字段都建了索引,事实表a表与维表a1,a2,a3,a4,a5关联的字段是否需要建相应的索引?
select a.*
from a
left join a1 on a.a = a1.a
left join a2 on a.b = a2.b
left join a3 on a.c = a3.c
left join a4 on a.d = a4.d
left join a5 on a.e = a5.e;
维表a1,a2,a3,a4,a5和事实表a关联的字段都建了索引,事实表a表与维表a1,a2,a3,a4,a5关联的字段是否需要建相应的索引?

Answer 1

都建的速度是快