Sql查询利用表变量优化一例

最近做的一个小项目，出租管理，需要计算租金，有点复杂，如下图

 

经过研究，写出代码如下：

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO

ALTER proc [dbo].[Expensedetails]
        @PID int,
        @PNE nvarchar(64)
as
--declare @Temp_A table(rank int null,projectID int null,ProjectName nvarchar(200) null,ProductName nvarchar(64) null,OrderDirection int null,orderdate smalldatetime null,subtotal decimal(18,2) null);
--declare @Temp_B table(rank int null,projectID int null,ProjectName nvarchar(200) null,ProductName nvarchar(64) null,OrderDirection int null,orderdate smalldatetime null,subtotal decimal(18,2) null, uday decimal(18,2) null,surplus decimal(18,2) null,counts decimal(18,2) null);
with t as (
select Row_Number() OVER ( ORDER by orderdate ASC) rank, a.ProjectID,a.ProjectName,a.ProductName,a.OrderDirection,a.OrderDate,sum(a.SubTotal) as SubTotal from (
select a.ID,a.ProjectID,b.ProjectName,a.ProductName,a.OrderDirection,a.OrderDate,a.SubTotal from (
select a.ID,b.ProductName,a.ProjectID,a.OrderDirection,a.OrderDate,a.SubTotal from (
select a.ID,a.ProjectID,b.StandardID,a.OrderDirection,a.OrderDate,b.SubTotal from SteelBusinessOrder a
join (select StandardID,sum(SubTotal) as SubTotal,OrderID from SteelBusinessList group by StandardID,OrderID) b
on a.ID = b.OrderID
) a
join SteelStandard b
on a.StandardID = b.ID and b.ProductName = @PNE
) a
join SteelProject b
on a.ProjectID = b.ID and b.ID = @PID
) a group by a.ID,a.ProjectID,a.ProjectName,a.ProductName,a.OrderDirection,a.OrderDate
)
--insert into @Temp_A select * from t;
with ts as (
select *,uday * surplus as counts from (
select  *,
(select DATEDIFF(d,(select OrderDate from @Temp_A a where a.rank = b.rank)
,case when((select  min(OrderDate) from @Temp_A a where a.rank > b.rank ) is null) then dateadd(d,1,getdate())
else (select  min(OrderDate) from @Temp_A a where a.rank>b.rank ) end)) as uday
,
isnull(
isnull((select sum(isnull(SubTotal,0)) from @Temp_A a where a.rank <= b.rank and OrderDirection = 0 ),0)
-
isnull((select sum(isnull(SubTotal,0)) from @Temp_A a where a.rank <= b.rank and OrderDirection = 1 ),0)
,0)
as surplus
from @Temp_A as b
) a
)
--insert into @Temp_B select * from ts
select rank,projectID,ProjectName,ProductName,OrderDirection,convert(char(10),orderdate,120) as orderdate,subtotal, uday,surplus,counts,(select SUM(counts) as zsum from @Temp_B  a where a.rank < = b.rank) as zsum,(case OrderDirection when 0 then '出库' when 1 then '入库' end) as Order_Direction   from @Temp_B  b

刚开始还行，数据一多就开始慢，29行数据达到了1.5秒，在网上问了几天也没有结果，自己在无意中看了下执行计划，只觉得自己的屏幕太小，非常复杂，后来看到是最后那个数据zsum有点问题，去掉了速度还可以，在网上又找了找，看到了表变量，果断在每个查询后面都以表变量存起来再用，就是上例中注释的部分，再执行，只有35ms，太好了~