MSSQL聯表查詢優化

       聯表查詢是數據庫系統常用的SQL方法，內聯查詢更是非常常見，如主表與明細查詢，當主從表數據不大時，直接內聯查詢，其性能是可以接受的，當數據記錄達到10萬級、百萬級、千萬級時，直接內聯查詢，其性能就難以接受了（超過2秒的查詢都會讓用戶很焦躁），特別是還有客戶端在同時寫操作，這裏可以看一下優化實例：

A、未優化前的MSSQL

-- =============================================
-- Author:		<baronyang>
-- Create date: <Create Date,,>
-- Description:	<未優化的SQL>
-- =============================================
Alter PROCEDURE dbo.存儲過程名
@ValNames NVARCHAR(max),			--變量名稱,多個用逗號隔開
@DispatchOrder NVARCHAR(50),			--派單號
@MachineNo	   NVARCHAR(50),			--機器編號
@bDate	NVARCHAR(20),					--開始日期
@eDate	NVARCHAR(20)					--結束日期
AS
SET NOCOUNT ON
DECLARE @sql NVARCHAR(max)='',@wherestr NVARCHAR(max)=''
DECLARE @ip NVARCHAR(50)=''
IF @DispatchOrder IS NOT NULL AND @DispatchOrder<>''
  SET @wherestr+=' And A.DispatchOrder='''+@DispatchOrder+''''
IF @MachineNo IS NOT NULL AND @MachineNo<>''
BEGIN
	SELECT @ip=IPAddr FROM DBO.CommunicationInfo WHERE MachineNo=@MachineNo
	IF @ip is NOT NULL AND @ip<>''
	  SET @wherestr+=' And A.ClientIP='''+@ip+''''
END
SET @bDate=CASE when ISNULL(@bDate,'')='' THEN CONVERT(VARCHAR(20),GETDATE(),120) else @bDate END
SET @eDate=CASE when ISNULL(@eDate,'')='' THEN CONVERT(VARCHAR(20),GETDATE(),120) else @eDate END
SET @wherestr+=' And A.UpLoadTime>='''+@bDate+''' And A.UpLoadTime<='''+@eDate+''''
CREATE TABLE #tmp (X INT,Y DECIMAL(18,2),legend NVARCHAR(200))
SET @sql='
insert into #tmp(X,legend,Y)
SELECT TotalNum AS X,ParaName AS legend,AVG(ParaValue) AS Y
FROM(
	SELECT A.TotalNum,b.ParaName,CAST(b.ParaValue AS decimal(18,2)) ParaValue
	from dbo.主表 A(nolock) inner JOIN dbo.明細表B(nolock)
	ON A.id=b.Pid
	WHERE  paraName in (select fname from  dbo.Fn_ListToTable('''+@ValNames+''','','')) '+@wherestr+'
) tt 
GROUP by TotalNum,ParaName '
print(@sql)
EXEC(@sql)
SELECT A.X,A.Y,B.VarName AS legend FROM #tmp A INNER JOIN dbo.SysItemList B(nolock)
ON A.legend=KebaVar

 A、優化後的MSSQL

Alter PROCEDURE dbo.存儲過程名
@ValNames NVARCHAR(max),					--變量名稱,多個用逗號隔開
@DispatchOrder NVARCHAR(50),			--派單號
@MachineNo	   NVARCHAR(50),			--機器編號
@bDate	NVARCHAR(20),					--開始日期
@eDate	NVARCHAR(20)					--結束日期
AS
SET NOCOUNT ON
DECLARE @sql NVARCHAR(max)='',@wherestr NVARCHAR(max)=''
DECLARE @ip NVARCHAR(50)=''
IF @DispatchOrder IS NOT NULL AND @DispatchOrder<>''
  SET @wherestr+=' And DispatchOrder='''+@DispatchOrder+''''
IF @MachineNo IS NOT NULL AND @MachineNo<>''
BEGIN
	SELECT @ip=IPAddr FROM DBO.CommunicationInfo WHERE MachineNo=@MachineNo
	IF @ip is NOT NULL AND @ip<>''
	  SET @wherestr+=' And ClientIP='''+@ip+''''
END
SET @bDate=CASE when ISNULL(@bDate,'')='' THEN CONVERT(VARCHAR(20),GETDATE(),120) else @bDate END
SET @eDate=CASE when ISNULL(@eDate,'')='' THEN CONVERT(VARCHAR(20),GETDATE(),120) else @eDate END
SET @wherestr+=' And UpLoadTime>='''+@bDate+''' And UpLoadTime<='''+@eDate+''''
declare @timewhere nvarchar(1000)=' And UpLoadTime>='''+@bDate+''' And UpLoadTime<='''+@eDate+''''
--臨時模次表
create table #tmpHistory (id int not null,TotalNum int)
declare @sql1 nvarchar(1000)='insert into #tmpHistory(id,TotalNum) select id,TotalNum from dbo.主表(nolock) where 1=1 '+@wherestr
exec(@sql1)
CREATE TABLE #tmp (X INT,Y DECIMAL(18,2),legend NVARCHAR(200))
SET @sql='
SELECT A.TotalNum,b.ParaName,CAST(b.ParaValue AS decimal(18,2)) ParaValue
	into #tmp2
	from #tmpHistory as A inner JOIN 
	(select pid,ParaName,ParaValue from dbo.明細表(nolock) 
		where pid in (select id from #tmpHistory)
			  And paraName in (select fname from  dbo.Fn_ListToTable('''+@ValNames+''','',''))
	) as B
	ON A.id=b.Pid
insert into #tmp(X,legend,Y)
SELECT TotalNum AS X,ParaName AS legend,AVG(ParaValue) AS Y
FROM #tmp2 GROUP by TotalNum,ParaName '
EXEC(@sql)
SELECT A.X,A.Y,B.VarName AS legend FROM #tmp A INNER JOIN dbo.SysItemList B(nolock)
ON A.legend=KebaVar
ORDER BY A.X

主表記錄達到6萬+，明細達到450萬+

未優化前表查詢響應時間10秒以前，優化後2秒以內完成；

優化的思路：先將主表的查詢範圍和結果欄位縮小並將結果寫入臨時表，然後將明細的結果集縮小，再使用內聯查詢，這樣查詢響應速度快且響應時間波動小；