--执行这个语句对比下面的，首先看结果一致不，然后看速度有没有变快
--记得清空缓存
/*
dbcc dropcleanbuffers   
dbcc freeproccache   
dbcc freesystemcache ('ALL','default');

--[语句执行花费时间(毫秒)]
declare @d datetime
set @d=getdate()
/*你的sql脚本开始*/

/*你的sql脚本结束*/
select [语句执行花费时间(毫秒)]=datediff(ms,@d,getdate()) 


*/
--1
select t0.SkuId , t0.SkuNo , t0.ProductNo, t0.ProductName, t3.StockId, t4.StockName   
PeriodIn,PeriodOut
from dbo.Prod_Sku AS t0 inner join dbo.Wms_LocStock AS t2 on t0.SkuId = t2.SkuId 
inner join dbo.Wms_Location AS t3 on t2.LocId = t3.LocId 
inner join dbo.Wms_WareHouse AS t4 on t3.StockId = t4.StockId
INNER JOIN /*如果结果不对，把这里改成left join 试试 */(
select skuId,StockId,
sum(CASE WHEN AddedQty>0 THEN AddedQty ELSE 0 END ) AS PeriodIn ,
sum(CASE WHEN AddedQty<0 THEN AddedQty ELSE 0 END ) AS PeriodOut ,
from dbo.Wms_StockLog
GROUP BY skuId,StockId
) AS t5 ON t0.skuId=t5.SkuId and t0.StockId=t5.StockId


-------------------------
--2
select t0.SkuId , t0.SkuNo , t0.ProductNo, t0.ProductName, t3.StockId, t4.StockName   

 ---下面2个花了7秒
--AddedQty 必须入库添加的商品数量 》0 必须+的表示 入库 《0 必须-的 出库
 ,(select sum(AddedQty)from dbo.Wms_StockLog where skuId=t0.SkuId and StockId=t3.StockId
  and AddedQty>0) as PeriodIn --入库数量   
 ,(select sum(AddedQty)from dbo.Wms_StockLog where skuId=t0.SkuId and StockId=t3.StockId
  and AddedQty<0 )as PeriodOut--出库数量

from dbo.Prod_Sku AS t0 inner join dbo.Wms_LocStock AS t2 on t0.SkuId = t2.SkuId 
inner join dbo.Wms_Location AS t3 on t2.LocId = t3.LocId 
inner join dbo.Wms_WareHouse AS t4 on t3.StockId = t4.StockId

------解决方案--------------------
如果确实想解决问题的话，把你的测试数据准备好，
提供表结构的详细说明，包括字段说明，每张表的主键、外键、索引情况，表的数据量大小，要达到的效果，等等，这样大家才好帮你。
只是给条sql语句，只能就语法层面分析，其它的一些因素是看不到的。
同时可以去看一下执行计划，那个是调优必看的东西。

------解决方案--------------------
你这是个查询吗？
建议  

,(select top 1 OldQty from dbo.Wms_StockLog where SkuId=t0.SkuId and StockId=t3.StockId