sql server ,查询数据很快，但是加上 order by后，很慢很慢。不加“order by CreatedTime DESC”时，查询是0.6S，加上后查询是19S。（关联表code，有几百万条数据，主表只有二十多条数据 ）请指教怎么优化这条sql？加了索引也不起任何作用。sql如下：
select LinesNo, PointNo, EmployeeNo, sioos.TraceCodeChar, BadContent, sioos.CreatedTime, svcc.Color, silb.Name,
case when State=0 then 'NG' when State=1 then 'OK' end as State,
case when State=1 then '否'
when State=0 and CheckState = 2 then '否'
when State=0 and CheckState = 0 then '否'
when State=0 and CheckState = 1 then '是'
end as IsOverKill
from station as sioos
left join code as svcc on sioos.TraceCodeChar = svcc.QrCodeChar
left join trace as sitr on sioos.TraceCodeChar = sitr.TraceCodeChar and sitr.StationNo = 'OQC'
left join linebody as silb on sitr.LineBodyNo = silb.LineBodyNo
where sioos.CreatedTime BETWEEN '2022/8/8 0:00:00' AND '2022/8/12 0:00:00'
order by sioos.CreatedTime DESC
explain的结果是什么
加索引不起作用，那你加的是什么索引，是给CreatedTime 列单独加的索引还是一个聚合索引
order by CreatedTime DESC没指明是哪个表的CreatedTime
这个你使用子查询 先排好序 之后在case when 和left join 呢? 不能肯定 你可以尝试下 .
(select 字段 from station as sioos order by sioos.CreatedTime DESC)a