什么是 VARCHAR(MAX) = NULL 和 fnStringSplit？答案

【问题标题】：What is VARCHAR(MAX) = NULL and fnStringSplit?什么是 VARCHAR(MAX) = NULL 和 fnStringSplit？
【发布时间】：2021-05-11 22:53:18
【问题描述】：

这是从存储过程中获取的。我不确定 where 语句后半部分的代码在做什么。 @DivisionList 在没有价值的情况下如何使用它？ fnStringSplit 是什么？任何帮助都会很棒。谢谢

    SET ANSI_NULLS ON
    GO
    SET QUOTED_IDENTIFIER ON
    GO
              
    ALTER  PROCEDURE [dbo].[spAppGetSAMDataForBARCValidationAudit]
@DivisionList VARCHAR(MAX) = NULL,
@RegionList VARCHAR(MAX) = NULL,
@PlanIDList VARCHAR(MAX) = NULL,
@LastUpdateByID CHAR(7),
@SyncType CHAR(15) = NULL
    AS
    BEGIN

BEGIN TRY
    IF (@SyncType = 'BARCtoMAAUI')
    BEGIN                       
        IF (SELECT  OBJECT_ID ('tempdb..#tmpTPFMRA2')) IS NOT NULL
        BEGIN
            DROP TABLE #tmpTPFMRA2;
        END;
        SELECT DISTINCT
               PlanYearID,
               CPS AS BidYearCPBPS,
               LastUpdateDateTime AS [date]
        INTO #tmpTPFMRA2
        FROM [dbo].[Trend_SavedPopulationBarcBidYearMembership] WITH (NOLOCK);

        IF (SELECT  OBJECT_ID ('tempdb..#tmpTPFMarketAdj2')) IS NOT NULL
        BEGIN
            DROP TABLE #tmpTPFMarketAdj2;
        END;
        SELECT DISTINCT
               CPS AS BidYearCPBPS,
               LastUpdateDateTime AS [date]
        INTO #tmpTPFMarketAdj2
        FROM [dbo].[Trend_SavedPopulationMarketAdjustment] WITH (NOLOCK);             

        --GET bidyear value 
        DECLARE @BidYear2 INT;
        SELECT @BidYear2 = dbo.fnGetBidYear();

        SELECT DISTINCT
               pl.PlanYear,
               pl.CPS,
               pl.LastCPS,
               ISNULL(pl.PlanInfoID, 0) PlanInfoID,
               pl.Division,
               pl.Region,
               pl.Product,
               pl.SNPType,
               pl.PlanType,
               ISNULL(pl.IsHidden, 0) IsHidden,
               ISNULL(cw.BidYear, 0) CWBidYear,
               cw.SSStateCountyCD,
               cw.BaseYearCPS,
               cw.CurrentYearCPS,
               cw.BidYearCPS,
               ISNULL(cw.ServiceAreaOptionID, 0) ServiceAreaOptionID,
               cw.ServiceAreaOptionName,
               cw.ServiceAreaOptionDescription,
               ISNULL(cw.BidYearRenewalTypeID, 0) BidYearRenewalTypeID,
               ISNULL(cw.BidYearPlanInfoID, 0) BidYearPlanInfoID,
               ISNULL(cw.CurrentYearPlanInfoID, 0) CurrentYearPlanInfoID,
               ISNULL(cw.IsActive, 0) IsActive,
               ISNULL(tpfMRA.[date], 0) AS MRALastUpdatedTime,
               ISNULL(tpfMarketAdj.[date], 0) AS MarketAdjLastUpdatedTime,                    
               @BidYear2 AS BidYear
       
        FROM vwPlanInfo pl WITH (NOLOCK)
            LEFT JOIN
            (
                SELECT DISTINCT
                       BidYear,
                       SSStateCountyCD,
                       BaseYearCPS,
                       CurrentYearCPS,
                       BidYearCPS,
                       ServiceAreaOptionID,
                       ServiceAreaOptionName,
                       ServiceAreaOptionDescription,
                       BidYearRenewalTypeID,
                       BidYearPlanInfoID,
                       CurrentYearPlanInfoID,
                       IsActive
                FROM vwSAMCrosswalks WITH (NOLOCK)
            ) cw
                ON pl.PlanInfoID = cw.BidYearPlanInfoID
                   AND pl.PlanYear = cw.BidYear                 
            LEFT JOIN #tmpTPFMRA2 tpfMRA WITH (NOLOCK)
                ON pl.PlanYear = tpfMRA.PlanYearID
                   AND pl.CPS = tpfMRA.BidYearCPBPS
            LEFT JOIN #tmpTPFMarketAdj2 tpfMarketAdj WITH (NOLOCK)
                ON pl.CPS = tpfMarketAdj.BidYearCPBPS                
        WHERE pl.PlanYear >
        (
            SELECT MIN(PlanYear) - 3
            FROM LkpPlanYear WITH (NOLOCK)
            WHERE IsProjectedYear = 1
        )
              AND
              (
                  (@DivisionList IS NULL)
                  OR pl.Division IN
                     (
                         SELECT Value FROM dbo.fnStringSplit(@DivisionList, ',')
                     )
              )
              AND
              (
                  (@RegionList IS NULL)
                  OR pl.Region IN
                     (
                         SELECT Value FROM dbo.fnStringSplit(@RegionList, ',')
                     )
              )
              AND
              (
                  (@PlanIDList IS NULL)
                  OR pl.PlanInfoID IN
                     (
                         SELECT DISTINCT Value FROM dbo.fnStringSplit(@PlanIDList, ',')
                     )
              );             
    END;

   ELSE
    BEGIN

        SELECT DISTINCT
               PlanYearID,
               CPS AS BidYearCPBPS,
               LastUpdateDateTime AS [date]
        INTO #tmpTPFMRA
        FROM [dbo].[Trend_SavedPopulationBarcBidYearMembership] WITH (NOLOCK);

        SELECT DISTINCT
               CPS AS BidYearCPBPS,
               LastUpdateDateTime AS [date]
        INTO #tmpTPFMarketAdj
        FROM [dbo].[Trend_SavedPopulationMarketAdjustment] WITH (NOLOCK);

        SELECT DISTINCT
               cs.PlanInfoID,
               cs.ServiceAreaOptionID,
               cs.BasePlanInfoID,
               cs.Status,
               cs.RemovedMM,
               cs.MovingMM,
               cs.TotalMM,
               cs.SignificancePct,
               cs.IsWks1BasePlan
        INTO #tmpCalcSign
        FROM dbo.CalcSignificance cs WITH (NOLOCK);

        --GET bidyear value 
        DECLARE @BidYear INT;
        SELECT @BidYear = dbo.fnGetBidYear();

        SELECT DISTINCT
               pl.PlanYear,
               pl.CPS,
               pl.LastCPS,
               pl.PlanInfoID,
               pl.Division,
               pl.Region,
               pl.Product,
               pl.SNPType,
               pl.PlanType,
               ISNULL(pl.IsHidden, 0) IsHidden,
               ISNULL(cw.BidYear, 0) CWBidYear,
               cw.SSStateCountyCD,
               cw.BaseYearCPS,
               cw.CurrentYearCPS,
               cw.BidYearCPS,
               ISNULL(cw.ServiceAreaOptionID, 0) ServiceAreaOptionID,
               cw.ServiceAreaOptionName,
               cw.ServiceAreaOptionDescription,
               ISNULL(cw.BidYearRenewalTypeID, 0) BidYearRenewalTypeID,
               ISNULL(cw.BidYearPlanInfoID, 0) BidYearPlanInfoID,
               ISNULL(cw.CurrentYearPlanInfoID, 0) CurrentYearPlanInfoID,
               ISNULL(cw.IsActive, 0) IsActive,
               ISNULL(rfi.PlanInfoID, 0) RollupPlanInfoID,
               rfi.ServiceAreaOptionID RollupSAOptionID,
               rfi.RollupName,
               ISNULL(tpfMRA.[date], 0) AS MRALastUpdatedTime,
               ISNULL(tpfMarketAdj.[date], 0) AS MarketAdjLastUpdatedTime,
               ISNULL(tmpCalcSign.PlanInfoID, 0) CalcPlanInfoID,
               ISNULL(tmpCalcSign.ServiceAreaOptionID, 0) CalcServiceAreaOptionID,
               ISNULL(tmpCalcSign.BasePlanInfoID, 0) CalcBasePlanInfoID,
               ISNULL(tmpCalcSign.Status, '') [Status],
               ISNULL(tmpCalcSign.RemovedMM, 0.0) RemovedMM,
               ISNULL(tmpCalcSign.TotalMM, 0.0) TotalMM,
               ISNULL(tmpCalcSign.MovingMM, 0.0) MovingMM,
               ISNULL(tmpCalcSign.SignificancePct, 0.0) SignificancePct,
               ISNULL(tmpCalcSign.IsWks1BasePlan, 0) IsWks1BasePlan,
               @BidYear AS BidYear

        --tmpCalcSign.Status,tmpCalcSign.RemovedMM,tmpCalcSign.TotalMM,tmpCalcSign.SignificancePct,tmpCalcSign.IsWks1BasePlan
        FROM vwPlanInfo pl WITH (NOLOCK)
            LEFT JOIN
            (
                SELECT DISTINCT
                       BidYear,
                       SSStateCountyCD,
                       BaseYearCPS,
                       CurrentYearCPS,
                       BidYearCPS,
                       ServiceAreaOptionID,
                       ServiceAreaOptionName,
                       ServiceAreaOptionDescription,
                       BidYearRenewalTypeID,
                       BidYearPlanInfoID,
                       CurrentYearPlanInfoID,
                       IsActive
                FROM vwSAMCrosswalks WITH (NOLOCK)
            ) cw
                ON pl.PlanInfoID = cw.BidYearPlanInfoID
                   AND pl.PlanYear = cw.BidYear
            LEFT JOIN
            (
                SELECT DISTINCT
                       PlanInfoID,
                       ServiceAreaOptionID,
                       RollupName
                FROM vwRollupForecastInfo WITH (NOLOCK)
            ) rfi
                ON pl.PlanInfoID = rfi.PlanInfoID
            LEFT JOIN #tmpTPFMRA tpfMRA WITH (NOLOCK)
                ON pl.PlanYear = tpfMRA.PlanYearID
                   AND pl.CPS = tpfMRA.BidYearCPBPS
            LEFT JOIN #tmpTPFMarketAdj tpfMarketAdj WITH (NOLOCK)
                ON pl.CPS = tpfMarketAdj.BidYearCPBPS
            LEFT JOIN #tmpCalcSign tmpCalcSign WITH (NOLOCK)
                ON pl.PlanInfoID = tmpCalcSign.PlanInfoID
        WHERE pl.PlanYear >
        (
            SELECT MIN(PlanYear) - 3
            FROM LkpPlanYear WITH (NOLOCK)
            WHERE IsProjectedYear = 1
        )
              AND
              (
                  (@DivisionList IS NULL)
                  OR pl.Division IN
                     (
                         SELECT Value FROM dbo.fnStringSplit(@DivisionList, ',')
                     )
              )
              AND
              (
                  (@RegionList IS NULL)
                  OR pl.Region IN
                     (
                         SELECT Value FROM dbo.fnStringSplit(@RegionList, ',')
                     )
              )
              AND
              (
                  (@PlanIDList IS NULL)
                  OR pl.PlanInfoID IN
                     (
                         SELECT DISTINCT Value FROM dbo.fnStringSplit(@PlanIDList, ',')
                     )
              );

    END;

END TRY
BEGIN CATCH

    DECLARE @ErrorMessage NVARCHAR(4000);
    DECLARE @ErrorSeverity INT;
    DECLARE @ErrorState INT;
    DECLARE @ErrorException NVARCHAR(4000);
    DECLARE @errSrc VARCHAR(MAX) = ISNULL(ERROR_PROCEDURE(), 'SQL'),
            @currentdate DATETIME = GETDATE();

    SELECT @ErrorMessage = ERROR_MESSAGE(),
           @ErrorSeverity = ERROR_SEVERITY(),
           @ErrorState = ERROR_STATE(),
           @ErrorException
               = N'Line Number :' + CAST(ERROR_LINE() AS VARCHAR) + N' .Error Severity :'
                 + CAST(@ErrorSeverity AS VARCHAR) + N' .Error State :' + CAST(@ErrorState AS VARCHAR);
    RAISERROR(@ErrorMessage, @ErrorSeverity, @ErrorState);

    ---Insert into app log for logging error------------------  
    EXEC spAppAddLogEntry @currentdate,
                          '',
                          'ERROR',
                          @errSrc,
                          @ErrorMessage,
                          @ErrorException,
                          @LastUpdateByID;
    ;

        END CATCH;
    END;

【问题讨论】：

fnStringSplit 是在您的 SQL Server 上定义的，因此只有您确定。按名称和用法，我猜它是一个自定义表值 UDF。当我用谷歌搜索它时，我得到了这个github.com/zgudino/mssql-toolkit/blob/master/FNStringSplit.sql 这是一个函数，它接受一个分隔字符串并将其拆分为行。更高版本的 SQL Server 内置了此功能
@DivisionList 在没有价值的情况下如何使用？ 正确。在您发布的代码中，它永远没有价值。必须有更多的代码。您发布的只是一个代码片段。从代码来看，它看起来像是一个 SP 参数。所有这些都是推测 - 发布完整代码
@Nick.McDermaid 我添加了完整的代码。谢谢你的帮助。尽管我可能会遗漏一些东西，但我仍然认为它不会在任何地方使用。你在 fnStringSplit 上是对的。很有帮助！
你真的不应该把NOLOCK 到处乱扔，这很危险，而且可能会返回完全错误的结果。这不是“更快”的开关

标签： sql-server-2008 ssms

【解决方案1】：

这些变量表示以逗号分隔的列表（一种将列表传递到查询中的基本方式），然后查询仅在列表中有任何内容时才进行过滤：

              (
                  (@DivisionList IS NULL)  -- either the list is empty
                  OR pl.Division IN
                     (
                         SELECT Value FROM dbo.fnStringSplit(@DivisionList, ',')
                         -- this seems to be a table function which splits the string by commas
                         -- the result of the function is like another view or table
                     )
              )

所以要么列表为空，要么列表中有匹配项。

如果没有fnStringSplit 的来源，我无法进一步说明，但它的性能可能并不好。在较新版本的 SQL Server 中，您可以改用 STRING_SPLIT，它的性能应该会更好。

更好的选择是传入一个实际的表值参数，这本质上是一个只读表变量。

那么代码如下：

              (
                  NOT EXISTS (SELECT 1 FROM @DivisionList)  -- either the list is empty
                  OR pl.Division IN
                     (
                         SELECT Value FROM @DivisionList
                         -- no need to split
                     )
              )

【讨论】：

嘿查理，感谢您的回复和帮助。从我发布的 SP 中，当他们唯一引用它是在定义变量的代码开头时，我怎么知道这个列表中有什么？
是个参数，是调用存储过程的人传入的