Question

我正在寻求在特定时间范围内从每个机构获得25条随机线路。这是我提出的一个脚本：

DECLARE @dateStart DATE,
        @dateEnd DATE,
        @agency varchar(8)

set @dateStart = '9/1/2016'
set @dateEnd = '9/30/2016'

IF OBJECT_ID('tempdb.dbo.#tmp_THISDATA', 'U') IS NOT NULL 
DROP TABLE #tmp_THISDATA

CREATE TABLE #tmp_THISDATA(
    [ACCOUNT] [varchar](30) NOT NULL,
    [AGENCY_CODE] [varchar](8) NOT NULL,
    [THE_DATE] [DATETIME] NOT NULL)

DECLARE agencies CURSOR FOR
SELECT DISTINCT [AGENCY_CODE]
FROM [dbo].[CORE_DATA] dial
WHERE CAST([THE_DATE] AS DATE) BETWEEN @dateStart AND @dateEnd

OPEN agencies
FETCH NEXT FROM agencies   
INTO @agency

WHILE @@FETCH_STATUS = 0  
BEGIN  

    INSERT INTO #tmp_THISDATA
    SELECT TOP 25
           [ACCOUNT]
          ,[AGENCY_CODE]
          ,[THE_DATE]
    FROM [dbo].[CORE_DATA] dial
    WHERE CAST([THE_DATE] AS DATE) BETWEEN @dateStart AND @dateEnd
      AND AGENCY_CODE = @agency
    ORDER BY NEWID()
END

SELECT *
FROM #tmp_THISDATA

这可行，但运行时间很长。这是一个丑陋的数据集，并且有一些优化它的努力，但我怀疑如果这样的事情是可行的，消除循环也会加速它。

可以消除循环吗？

Answer 1

您可以使用ROW_NUMBER窗口功能

INSERT INTO #tmp_THISDATA
SELECT [ACCOUNT],
       [AGENCY_CODE],
       [THE_DATE]
FROM   (SELECT Row_number()OVER(partition BY AGENCY_CODE ORDER BY Newid() ) AS rn,
               [ACCOUNT],
               [AGENCY_CODE],
               [THE_DATE]
        FROM   [dbo].[CORE_DATA] dial
        WHERE  [THE_DATE] > dateadd(dd,-1,@dateStart) and [THE_DATE] <= @dateEnd) a
WHERE  rn <= 25

Answer 2

您也可以使用CROSS APPLY

Select Distinct A.Account
      ,B.Agency_Code
      ,B.The_Date
 From  [dbo].[CORE_DATA] A
 Cross Apply (Select Top 25 Agency_Code,Agency_Code 
               From  [dbo].[CORE_DATA] 
               Where Account=A.Account and The_Date between @dateStart AND @dateEnd
               Order By NewID()
              ) B

来自每个组的行的随机x计数而没有循环

2 个答案: