避免 WHILE 循环和 CURSOR 以获得更好的性能？

Question

我想知道是否有人可以帮助简化此过程 - 并提高性能...！？

我们有关于赠款的数据。 'Donors' 向'Recipients' 提供资金，我们希望显示每个捐助者在 3 个时期内的前 15 名受助人：CurrentYear-20、CurrentYear-10 和 CurrentYear。我们发布年度报告并显示每个捐助者在 World 和 GeoZone 总数中所占的百分比。

我已经“继承”了这段由我的一位前任编写的代码。在我们切换到使用视图之前，执行时间大约是 15-30 分钟。目前，这将在不到 4 小时内运行（计划为服务器代理作业）！管理层不高兴。由于各种原因，该视图必须继续使用，目前只有不到 900,000 行包含 1950 年代以后的数据。我们目前为 30 个（大）捐助者运行此报告，并且每年都会增加更多。

为了帮助提高性能，我考虑过使用 CTE 或/使用 SUM() OVER(Partition BY...) 或这些的组合，但我不确定如何去做。

有人能指出我正确的方向吗？

流程如下：

• 创建一个表格（变量）来保存当前捐赠者的前 15 名收件人
• 创建一个表（变量）来保存捐赠者列表
• 按照捐赠者在报告中出现的顺序填充捐赠者表
• 循环遍历供体表并针对每个供体：
  • 将此捐助者的捐助者 ID 放入临时表中
  • 循环 3 次（针对 CurrentYear-20、CurrentYear-10、CurrentYear）
  • 计算 18 个区域/区域中每个区域的份额总数
  • 打印报告中每个部分的值
• 获取下一个捐赠者 ID

您可以从上面看到，每个捐赠者的计算都运行了 54 次 (18x3)！

这里是代码（简化）：

-- @LatestYear is passed as a parameter, hardcoded here for simplicity
DECLARE @LatestYear SMALLINT ,
    @CurrentYear SMALLINT ,
    @DonorID SMALLINT ,
    @totalWorld NUMERIC(10, 2) ,
    @LoopCounter TINYINT ,
    @DonorName VARCHAR(100)  
SELECT  @latestyear = 2012  

    -- create a table to hold list of top 15 recipients for each donor and their 'share' of ODA.  
DECLARE @Top15 TABLE
(
  Country VARCHAR(100) ,
  Percentage REAL
)  

    -- create a table to hold list of donors, ordered as they need to appear in the report.  
DECLARE @PageOrder TABLE
(
  DonorID SMALLINT ,
  DonorName VARCHAR(100) ,
  SortOrder SMALLINT IDENTITY(1, 1)
)

    -- create a table to store the "focus" donor.  
DECLARE @CurrentDonor TABLE ( DonorID SMALLINT )

INSERT  INTO @PageOrder
        SELECT  DonorID ,
                DonorName
        FROM    dbo.LookupDonor
        ORDER BY DonorName;  

    -- cursor to loop through the donors in SortOrder
DECLARE DonorCursor CURSOR
FOR
    SELECT  DonorID ,
            DonorName
    FROM    @PageOrder
    ORDER BY DonorName;
OPEN DonorCursor
FETCH NEXT FROM DonorCursor INTO @DonorID, @DonorName

WHILE @@fetch_status = 0 
    BEGIN

        INSERT  INTO pubOutput
                ( XMLText )
                SELECT  @DonorName;

    -- Populate the DonorID table
        INSERT  INTO @CurrentDonor
        VALUES  ( @DonorID )

    /* The following loop is invoked 3 times. The first time through, the year will be 20 years before the latest year,
    the second time through, 10 years before. The last time through the year will be the latest year.
    */

        SET @LoopCounter = 1
        WHILE @LoopCounter <= 3 
            BEGIN
                SELECT  @CurrentYear = CASE @LoopCounter
                                         WHEN 1 THEN @LatestYear - 20
                                         WHEN 2 THEN @LatestYear - 10
                                         ELSE @LatestYear
                                       END

        -- calculate the world total for the current years (year,year-1) for all recipients
                SELECT  @totalWorld = SUM(Amount)
                FROM    dbo.vData2 d
                        INNER  JOIN ( SELECT    RecipientID
                                      FROM      dbo.RecipientGroup
                                      WHERE     GroupID = 160
                                    ) c ON d.RecipientID = c.RecipientID
                        INNER  JOIN @CurrentDonor z ON d.DonorID = z.DonorID
                WHERE   d.year IN ( @CurrentYear - 1, @CurrentYear )

        -- calculate the GeoZones total for the current years (year,year-1) 
                SELECT  @totalGeoZones = SUM(Amount)
                FROM    dbo.vDac2a d
                        INNER  JOIN ( SELECT    RecipientID
                                      FROM      dbo.GeoZones
                                      WHERE     GeoZoneID = 100
                                    ) x ON d.RecipientID = x.RecipientID
                        INNER  JOIN @CurrentDonor z ON d.DonorCode = z.DonorCode
                WHERE   d.year IN ( @CurrentYear - 1, @CurrentYear )

        -- Find the top 15 recipients for the current donor
                INSERT  INTO @Top15
                        SELECT TOP 15
                                r.RecipientName ,
                                ( ISNULL(SUM(Amount), 0) / @totalWorld ) * 100
                        FROM    dbo.vData2 d
                                INNER JOIN dbo.LookupRecipient r ON r.RecipientID = d.RecipientID
                                INNER JOIN @CurrentDonor z ON d.DonorID = z.DonorID
                        WHERE   d.year IN ( @CurrentYear - 1, @CurrentYear )
                        GROUP BY r.RecipientName
                        ORDER BY 2 DESC

        -- Print the top 15 recipients and total
                INSERT  INTO pubOutput
                        (
                          XMLText
                        )
                        SELECT  country + @Separator + CAST(percentage AS VARCHAR)
                        FROM    @Top15
                        ORDER BY percentage DESC
                INSERT  INTO pubOutput
                        (
                          XMLText
                        )
                        SELECT  @Heading1 + @Separator + CAST(SUM(Percentage) AS VARCHAR)
                        FROM    @Top15

    -- Breakdown by Regionas
        -- Region1
                IF @totalWorld IS NOT NULL 
                    INSERT  INTO pubOutput
                            (
                              XMLText
                            )
                            SELECT  'Region1' + @Separator
                                    + CAST(( ISNULL(SUM(Amount), 0) / @totalWorld ) * 100 AS VARCHAR)
                            FROM    dbo.vData2 d
                                    INNER JOIN ( SELECT RecipientID
                                                 FROM   dbo.RecipientGroup
                                                 WHERE  RegionID = 1
                                               ) c ON d.RecipientID = c.RecipientID
                                    INNER JOIN @CurrentDonor z ON d.DonorID = z.DonorID
                            WHERE   d.year IN ( @CurrentYear - 1, @CurrentYear )

                ELSE    -- force output of sub-total heading
                    INSERT  INTO pubOutput
                            (
                              XMLText
                            )
                            SELECT  @Heading2 + @Separator + '--'

        -- Region2-8
        /* similar syntax as Region1 above, for all Regions 2-8 */

        -- Total Regions
                INSERT  INTO pubOutput
                        (
                          XMLText
                        )
                        SELECT  @Heading2 + @Separator + CAST(@totalWorld AS VARCHAR)

    -- Breakdown by GeoZones 1-7
        -- GeoZone1
                INSERT  INTO pubOutput
                        (
                          XMLText
                        )
                        SELECT  'GeoZone1' + @Separator
                                + CAST(( ISNULL(SUM(Amount), 0) / @totalGeoZones ) * 100 AS VARCHAR)
                        FROM    dbo.vDac2a d
                                INNER JOIN ( SELECT RecipientID
                                             FROM   dbo.GeoZones
                                             WHERE  GeoZoneID = 1
                                           ) m ON d.RecipientID = m.RecipientID
                                INNER JOIN @CurrentDonor z ON d.DonorCode = z.DonorCode
                        WHERE   d.year IN ( @CurrentYear - 1, @CurrentYear )

        -- GeoZones2-8
        /* similar syntax as GeoZone1 above for GeoZones 2-7 */

        -- Total GeoZones - currently hard-coded as 100, due to minor rounding errors
                INSERT  INTO pubOutput
                        (
                          XMLText
                        )
                        SELECT  @Heading3 + @Separator + '100'

                SET @LoopCounter = @LoopCounter + 1

            END -- year loop

    -- Get the next donor from the cursor
        FETCH NEXT FROM DonorCursor 
    INTO @DonorID, @DonorName

    END
 -- donorcursor

    -- Cleanup
CLOSE DonorCursor
DEALLOCATE DonorCursor

非常感谢您提供的任何帮助。

Answer 1

避免光标是必须的。您可以使用 'while' 代替光标。不过考虑到查询的复杂性，此时请保持光标不变。

要以其他方式提高性能，请检查以下查询的记录数：

1. 从 dbo.RecipientGroup WHERE GroupID=160 中选择 RecipientCode
2. 从 dbo.GeoZones WHERE GeoZoneID=100 中选择 RecipientCode
3. 从 dbo.RecipientGroup WHERE RegionID=1 中选择 RecipientID

我建议在游标“外部”为上述查询创建 3 个临时表，并在游标内部使用它们。

希望这会有所帮助！