如何减少SQL Server中的查询运行时间？

2019年7月20日 189次阅读

我写了下面的查询来从两个不同的表中检索不同的RegNo.但是在查询下面需要将近25秒来检索结果.在库存表中,有超过150万条记录.

Select F.PKID, F.RegNo
From
(
  Select E.PKID, E.RegNo 
  Row_Number() Over(Order By E.RegNo Asc) RowNo
  From
  (
    Select C.PKID, C.RegNo
    From
    (
      Select Pk_Id PKID, LTrim(RTrim(A.Reg_No)) RegNo, 
      Row_Number() Over(Partition By LTrim(RTrim(A.Reg_No)) 
      Order By (Select Null)) RegRowNo
      From dbo.KeyreferenceDetails A (NoLock)
      Where A.KeyreferenceStatus = 'L' 
      And A.Reg_No Like @Value And IsNull(Reg_No, '') <> '' And Not Exists
      (
        Select 1 From dbo.INVENTORY B (NoLock) 
        Where A.Reg_No = B.Inv_H_Reg_No
      ) 
    ) C
    Where C.RegRowNo = 1 And IsNull(C.RegNo, '') <> '-'
    Union
    Select D.PKID, D.RegNo
    From 
    (
      Select Pk_ID PKID, LTrim(LTrim(Txt_RegNo)) RegNo, 
      Row_Number() Over(Partition By LTrim(LTrim(A.Txt_RegNo)) 
      Order By (Select Null)) RegRowNo
      From dbo.MobileMessageDetails A (Nolock)  
      Left Join dbo.PLACE P (Nolock) On P.Place_Shrt_Code  = A.Txt_YarddCode 
      And P.[Status] = 'L'
      Left Join dbo.INVENTORY B (Nolock) On A.Txt_RegNo = B.Inv_H_Reg_No            
      Where A.Txt_INOUT In('IN', 'MOBILE') And IsNull(A.Txt_RegNo, '') <> '' And B.Inv_H_Pk_Id Is Null 
      And A.[Status] = 'L' And Txt_RegNo Like @Value 
    ) D
    Where D.RegRowNo = 1 And IsNull(D.RegNo, '') <> '-'
 ) E
) F
Where F.RowNo > 0 And F.RowNo <= 20

查询计划：

《如何减少SQL Server中的查询运行时间？》

可用指数：

KeyreferenceDetails表：

 Index Name ---------------+ Column Name ----------------- + Index Type
 IX_KeyreferenceDetails_I  |  Reg_No                       | NONCLUSTERED   
 IX_KeyreferenceDetails_II |  KeyreferenceStatus           | NONCLUSTERED

库存表：

 Index Name ---------------+ Column Name ----------------- + Index Type
 IX_Inventory_I            | Inv_H_Reg_No                  | NONCLUSTERED

MobileMessageDetails表：

 Index Name --------------- + Column Name ----------------- + Index Type
 IX_MobileMessageDetails_I  | Txt_RegNo                     | NONCLUSTERED
 IX_MobileMessageDetails_II | Txt_INOUT                     | NONCLUSTERED

放置表：

 Index Name ---------------+ Column Name ----------------- + Index Type
 IX_Place_I                | Place_Shrt_Code               | NONCLUSTERED  
 IX_Place_I                | Status                        | NONCLUSTERED

我在上面的查询中为所有使用的表创建了必需的索引.但查询成本很高.如何减少SQL Server中的查询运行时间？

统计输出：

SQL Server Execution Times:
CPU time = 0 ms,  elapsed time = 0 ms.
Table 'INVENTORY'. Scan count 6, logical reads 382, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'KeyreferenceDetails'. Scan count 15, logical reads 9062, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Mobile_MessageDetails'. Scan count 1, logical reads 4, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table '#TempItemsCount_____________________________________________________________________________________________________0000000118A9'. Scan count 0, logical reads 1, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

SQL Server Execution Times:
CPU time = 20733 ms,  elapsed time = 7844 ms.
Table 'INVENTORY'. Scan count 6, logical reads 382, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'KeyreferenceDetails'. Scan count 14, logical reads 9062, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Mobile_MessageDetails'. Scan count 1, logical reads 4, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table '#VehicleRegDetails__________________________________________________________________________________________________0000000118AB'. Scan count 0, logical reads 20, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

SQL Server Execution Times:
CPU time = 21139 ms,  elapsed time = 8146 ms.
Table '#TABLE_SCHEMA_______________________________________________________________________________________________________0000000118AA'. Scan count 0, logical reads 1, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

更新：

Insert Into #TempItemsCount(TotalCount)
Select Count(E.PKID)
From
 (
   Select E.PKID, E.RegNo 
      Row_Number() Over(Order By E.RegNo Asc) RowNo
      From
      (
        Select C.PKID, C.RegNo
        From
        (
          Select Pk_Id PKID, LTrim(RTrim(A.Reg_No)) RegNo, 
          Row_Number() Over(Partition By LTrim(RTrim(A.Reg_No)) 
          Order By (Select Null)) RegRowNo
          From dbo.KeyreferenceDetails A (NoLock)
          Where A.KeyreferenceStatus = 'L' 
          And A.Reg_No Like @Value And IsNull(Reg_No, '') <> '' And Not Exists
          (
            Select 1 From dbo.INVENTORY B (NoLock) 
            Where A.Reg_No = B.Inv_H_Reg_No
          ) 
        ) C
        Where C.RegRowNo = 1 And IsNull(C.RegNo, '') <> '-'
        Union
        Select D.PKID, D.RegNo
        From 
        (
          Select Pk_ID PKID, LTrim(LTrim(Txt_RegNo)) RegNo, 
          Row_Number() Over(Partition By LTrim(LTrim(A.Txt_RegNo)) 
          Order By (Select Null)) RegRowNo
          From dbo.MobileMessageDetails A (Nolock)  
          Left Join dbo.PLACE P (Nolock) On P.Place_Shrt_Code  = A.Txt_YarddCode 
          And P.[Status] = 'L'
          Left Join dbo.INVENTORY B (Nolock) On A.Txt_RegNo = B.Inv_H_Reg_No            
          Where A.Txt_INOUT In('IN', 'MOBILE') And IsNull(A.Txt_RegNo, '') <> '' And B.Inv_H_Pk_Id Is Null 
          And A.[Status] = 'L' And Txt_RegNo Like @Value 
        ) D
        Where D.RegRowNo = 1 And IsNull(D.RegNo, '') <> '-'
    ) E
 )

最佳答案 回答没有架构和有限的信息,因此不保证这将解析,但下面是尝试优化它,以便您至少可以理解这些方法.

优化可以分为几点：

>将复杂查询分离为更易于理解的单独语句(对于人和优化程序),并且已知优化程序可以很好地使用.例如,很容易优化第一个查询,因为很明显Reg_No用在JOIN和WHERE子句中.示例索引可能是：

CREATE NONCLUSTERED INDEX index_name ON dbo.KeyreferenceDetails(Reg_No)INCLUDE(Pk_Id,KeyreferenceStatus)WHERE KeyreferenceStatus =’L’
>消除JOIN,WHERE,PARTITION BY中的函数(ISNULL,COALESCE,LTRIM,RTRIM等).例如,考虑一下：

在哪里ISNULL(A.Reg_No,”)<> “”

优化器将无法在Reg_No上使用索引,因为您正在向其应用函数.相反,将其重写为：

在哪里A.Reg_No<> ”和A.Reg_No不是NULL
>考虑使用UNION ALL vs UNION.对于UNION,查询引擎将对两个集进行重复数据删除,并仅返回唯一身份验证.它必须在返回任何数据进行处理之前执行此操作.使用UNION ALL,您可以单独处理两个查询并将第二个集合附加到第一个集合的末尾.
>不是在WHERE子句中使用IN,而是可以使用LEFT OUTER JOIN并添加一个检查,以查看连接表中的键列是否为NULL以确保没有从它返回记录,或者是EXISTS,这将是通常表现得更有效率.

下面是将一些原则应用于查询的一种方法示例：

IF OBJECT_ID('tempdb..#temp') IS NOT NULL DROP TABLE #temp;
GO
SELECT  PKID = Pk_Id, 
        RegNo = LTrim(RTrim(A.Reg_No)), 
        RegRowNo = Row_Number() Over(Partition By LTrim(RTrim(A.Reg_No)) Order By (Select Null))
INTO    #temp
FROM    dbo.KeyreferenceDetails A WITH(NOLOCK)
        LEFT OUTER JOIN dbo.INVENTORY B WITH(NOLOCK) ON A.Reg_No = B.Inv_H_Reg_No
WHERE   B.Inv_H_Reg_No IS NULL
AND     A.KeyreferenceStatus = 'L' 
And     A.Reg_No Like @Value 
And     A.Reg_No IS NOT NULL
AND     A.Reg_No <> '';

INSERT INTO #temp (PKID, RegNo, RegRowNo)
  SELECT  PKID = Pk_ID, 
          RegNo = LTrim(LTrim(A.Txt_RegNo)), 
          RegRowNo = Row_Number() Over(Partition By LTrim(LTrim(A.Txt_RegNo)) Order By (Select Null)) 
  FROM    dbo.MobileMessageDetails A WITH(NOLOCK)
          LEFT OUTER JOIN dbo.PLACE P WITH(NOLOCK) ON P.Place_Shrt_Code  = A.Txt_YarddCode AND P.[Status] = 'L'
          LEFT OUTER JOIN dbo.INVENTORY B WITH(NOLOCK) ON A.Txt_RegNo = B.Inv_H_Reg_No            
  WHERE   B.Inv_H_Pk_Id Is Null 
  AND     A.Status = 'L' 
  AND     A.Txt_RegNo Like @Value 
  And     A.Txt_RegNo IS NOT NULL
  AND     A.Txt_RegNo <> ''
  AND     A.Txt_INOUT In ('IN', 'MOBILE');

IF OBJECT_ID('tempdb..#final') IS NOT NULL DROP TABLE #final;
GO
SELECT  t.PKID, 
        t.RegNo,
        RowNo = Row_Number() Over(Order By t.RegNo Asc)
INTO    #final
FROM    #temp t;
WHERE   t.RegNo <> '-'

SELECT  F.PKID, F.RegNo
FROM    #final F
WHERE   F.RowNo BETWEEN 1 AND 20

GO
DROP TABLE #temp, #final

由于此时很可能存在语法错误,因此当您查看此错误时,我建议您一次运行每个部分并确保其正常工作,而不是一次执行整个脚本.希望这可以帮助！

问候,

罗斯

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