sql - 为什么排序要花费我 70%？

Question

我的观点很慢：

ALTER  view [dbo].[TAT] as
WITH d AS ( SELECT TAT = CASE WHEN TAT > 191 THEN 192 ELSE TAT END,
   [MONTH entered],
   [YEAR] = DATEPART(yyyy,[datetime entered])
  FROM [SalesDWH].[dbo].[TurnAround] TurnAround
  left outer join hermes.lom.dbo.lom_specimen Lom
  on TurnAround.[specimen id] = lom.specimen
  LEFT outer join SalesDWH.dbo.Isomers Isomers
  on TurnAround.[specimen id] = Isomers.[accession id]
  WHERE lom.specimen is null
  and isomers.[accession id] is null
 -- GROUP BY CASE WHEN TAT > 191 THEN 192 ELSE TAT END 
    --[datetime entered],[Month Entered]
),
n AS ( SELECT TOP (192) n = ROW_NUMBER() OVER (ORDER BY [object_id]) 
  FROM sys.all_columns ORDER BY [object_id]
)
SELECT TAT = n.n,

  [MONTH entered],
  [YEAR]

FROM n LEFT OUTER JOIN d 
ON n.n = d.TAT  



GO

当我查看执行计划时，它告诉我其中一个步骤是 SORTING 花费了我 70%。

当我检查 SORTING 步骤时，它说我的 ORDER BY 是：

[SalesDWH].[dbo].[QuickLabDump].Specimen ID Ascending, [SalesDWH].[dbo].[QuickLabDump].Date Entered Ascending, [SalesDWH].[dbo].[QuickLabDump].Time Entered Ascending, [SalesDWH].[dbo].[QuickLabDump].Date Completed Ascending, [SalesDWH].[dbo].[QuickLabDump].Time Completed Ascending, [SalesDWH].[dbo].[QuickLabDump].Practice Name Ascending, [SalesDWH].[dbo].[QuickLabDump].Practice Code Ascending, [SalesDWH].[dbo].[QuickLabDump].Order Count Ascending, [SalesDWH].[dbo].[QLMLISMapping].MLIS Practice ID Ascending, [SalesDWH].[dbo].[adjustedtime].TimeDifference Ascending

但我没有在任何地方指定 ORDER BY。

问题：

如果我没有任何 ORDER BY，为什么会显示 ASCENDING for ORDER BY？
如何加快查看速度？

我不知道是否需要此信息，但上面的视图正在查询另一个名为TURNAROUND：

USE [SalesDWH]
GO

/****** Object:  View [dbo].[TurnAround]    Script Date: 05/25/2012 15:32:08 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO




ALTER VIEW [dbo].[TurnAround]
AS
SELECT     dbo.QuickLabDump.[Specimen ID], DATEPART(yyyy, dbo.QuickLabDump.[Date Entered]) AS [Year Entered], CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) 
                      AS DATETIME) + CAST(dbo.QuickLabDump.[Time Entered] AS TIME) AS [DateTime Entered], CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) 
                      + CAST(dbo.QuickLabDump.[Time Completed] AS TIME) AS [DateTime Completed], dbo.QuickLabDump.[Practice Code] AS [QL Practuce Code], 
                      dbo.QLMLISMapping.[MLIS Practice ID], DATEPART(m, dbo.QuickLabDump.[Date Entered]) AS [Month Entered], ROUND(CAST(DATEDIFF(mi, 
                      CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) AS DATETIME) + CAST(dbo.QuickLabDump.[Time Entered] AS TIME), 
                      CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) + CAST(dbo.QuickLabDump.[Time Completed] AS TIME)) AS FLOAT) / 60, 0) AS TAT, 
                      ROUND(CAST(DATEDIFF(mi, CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) AS DATETIME) + CAST('9:00AM' AS TIME), 


                      CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) 
                      + CAST(dbo.QuickLabDump.[Time Completed] AS TIME)) AS float) / 60, 0) 

                      AS [Hours TurnAround Since 9AM], TAT9AMStateAdjusted=                   



                      ROUND(CAST(DATEDIFF(mi, CAST(CAST(dbo.QuickLabDump.[Date Entered] AS DATE) AS DATETIME) 
                      + CAST('9:00AM' AS TIME),                                            
                      CAST(CAST(dbo.QuickLabDump.[Date Completed] AS DATE) AS DATETIME) 
                      + CAST(dbo.QuickLabDump.[Time Completed] AS TIME)) AS float) / 60, 0)                         


                      +dbo.adjustedtime.timedifference
                      ,dbo.QuickLabDump.[Order Count], CONVERT(VARCHAR(8), DATEADD(D, - (1 * DATEPART(dw, dbo.QuickLabDump.[Date Entered])) + 6,
                       dbo.QuickLabDump.[Date Entered]), 1) AS [Week Ending]
FROM         dbo.QuickLabDump 
             INNER JOIN dbo.QLMLISMapping 
             ON dbo.QuickLabDump.[Practice Code] = dbo.QLMLISMapping.[Quicklab ID]
             left outer join dbo.AccountState
             on dbo.QuickLabDump.[Practice Code]=dbo.AccountState.[Account]
             left outer join dbo.AdjustedTime 
             ON dbo.AccountState.[state]=dbo.adjustedtime.[state]
WHERE     (dbo.QuickLabDump.[Practice Code] NOT LIKE 'test%') AND (dbo.QuickLabDump.[Specimen ID] NOT LIKE 'of%') AND (dbo.QuickLabDump.Outcome <> 'rejected')
GROUP BY dbo.QuickLabDump.[Specimen ID], dbo.QuickLabDump.[Date Entered], dbo.QuickLabDump.[Time Entered], dbo.QuickLabDump.[Date Completed], 
                      dbo.QuickLabDump.[Time Completed], dbo.QuickLabDump.[Practice Name], dbo.QuickLabDump.[Practice Code], dbo.QuickLabDump.[Order Count], 
                      dbo.QLMLISMapping.[MLIS Practice ID],dbo.adjustedtime.timedifference
HAVING      (dbo.QuickLabDump.[Order Count] = MAX(dbo.QuickLabDump.[Order Count])) OR
                      (dbo.QuickLabDump.[Order Count] IS NULL)




GO

以下是表定义：

CREATE TABLE [dbo].[QuickLabDump](
    [Specimen ID] [varchar](50) NULL,
    [Client Key] [int] NULL,
    [Outcome] [varchar](50) NULL,
    [Medications] [varchar](max) NULL,
    [Date Collected] [date] NULL,
    [Time Collected] [time](0) NULL,
    [Date Entered] [date] NULL,
    [Time Entered] [time](0) NULL,
    [Date Completed] [date] NULL,
    [Time Completed] [time](0) NULL,
    [Test Date] [date] NULL,
    [Test Time] [time](0) NULL,
    [Practice Name] [varchar](500) NULL,
    [Practice Code] [varchar](50) NULL,
    [Requesting Physician] [varchar](500) NULL,
    [Other Medications] [varchar](max) NULL,
    [Order Comments] [varchar](max) NULL,
    [Reference Number] [varchar](500) NULL,
    [Order Count] [int] NULL,
    [QuickLabDumpID] [int] NOT NULL,
    [Source] [varchar](50) NULL,
    [MLIS] [varchar](50) NULL,
 CONSTRAINT [PK_QuickLabDump_1] PRIMARY KEY CLUSTERED 
(
    [QuickLabDumpID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

score 2 · Accepted Answer

您看到已排序的列是 TurnAroundGROUP BY子句中的列。执行 a 的最简单方法GROUP BY是首先按组列排序，然后按组拆分行，最后计算每个组的聚合，在这种情况下，看起来这正是数据库正在做的事情。

score 2 · Accepted Answer

您的 group by 和（外部）连接可能是排序的原因，您正在使用的列上是否有任何匹配的索引？如果您发布表的完整定义（包括索引和键/约束），那么找到问题的猜测就会减少。

score 2 · Accepted Answer

查询分析器向您显示在您的 Group BY 上进行排序。

您应该在 group by 正在使用的字段上测试\创建索引以提高性能。

这是有关 Group By 如何创建排序的更详细说明。关联

score 1 · Accepted Answer

只是为了确保你知道，我看到一个订单：

,
n AS ( SELECT TOP (192) n = ROW_NUMBER() OVER (ORDER BY [object_id]) 
  FROM sys.all_columns ORDER BY [object_id]
)

sql - 为什么排序要花费我 70%？

4 回答 4

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