最近项目中出现这样的情况，TestA 表左连接 TestB表，前台查询结果显示出现多条重复记录，经查询数据库得知，TestB中确实有符合条件的记录。

原脚本如下：

select  t1.*,t2.*
from TestA t1  
left outer join  TestB t2 
on t1.ch = t2.ch  and t2.DateTime >= '20170320000000' and t2.DateTime <= '20170330000000' 
where t1.cc='E170328097' 

改写后脚本如下：

select  t1.*,t2.*
from TestA t1  
left outer join  TestB t2 
on t1.ch = t2.ch  
where t1.cc='E170328097' 
and t2.id in (select max(id) from TestB t3 where ch = t1.ch and t3.DateTime >= '20170320000000' and t3.DateTime <= '20170330000000' )