Question

I have a view that is very slow:

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

When I look at the execution plan, it tells me that that one of the steps which is SORTING costs me 70%.

When I inspect the SORTING step it says my ORDER BY is:

[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

But I haven’t specified an ORDER BY anywhere.

Questions:

1. Why does it say ASCENDING for ORDER BY if I don’t have any ORDER BY’s?
2. How do I speed this view up?

I don’t know if this information is needed, but the above view is querying another view called 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

Here are the table definitions:

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]

Answer 1

The query analyzer is showing you that the sorting is occurring on your Group BY.

You should test\create indexes on the fields that the group by is using in order to increase performance.

Here is more detailed explanation on how Group By can create sorting. Link