相关疑难解决方法(0)

我有以下MySql查询:

select t1.*
from Table1 t1
inner join Table2 t2
on t1.CommonID = t2.CommonID
where t1.FilterID = 1

运行大约需要30秒,这很奇怪,因为如果我注释掉连接或where子句,它需要不到一秒钟:即

select t1.*
from Table1 t1
where t1.FilterID = 1

要么

select t1.*
from Table1 t1
inner join Table2 t2
on t1.CommonID = t2.CommonID

每个不到一秒钟.

然后是STRAIGHT_JOIN关键字,我可以在这里找到一个参考:http: //dev.mysql.com/doc/refman/5.0/en/join.html

STRAIGHT_JOIN类似于JOIN,只是左表始终在右表之前读取.这可以用于连接优化器以错误顺序放置表的那些(少数)情况.

什么？我可以写:

select t1.*
from Table1 t1
STRAIGHT_JOIN  Table2 t2
on t1.CommonID = t2.CommonID
where t1.FilterID = 1

并且查询在不到一秒的时间内执行.

更奇怪的是,我可以写:

select STRAIGHT_JOIN  t1.*
from Table1 t1
inner join Table2 t2
on t1.CommonID = …