SQL 中存在 IF 的正确用法

Question

我正在尝试运行下面的SQL声明

    select  FB.FundingSourceID,
          FB.FiscalYearID,
          (FB.FundingBudget-CA.CurrentAmount-DE.CFOApproved) as Amount from    
           (select 
            FundingSourceID, 
            FiscalYearID, 
            SUM(COALESCE(Amount,0)) as FundingBudget 
           from [cap].[FactFundingSourceBudget]
           WHERE IsDeleted = 0
           group by FundingSourceID, FiscalYearID) AS FB

LEFT JOIN (
           select 
            FundingSourceID, 
            FiscalYearID, 
            SUM(COALESCE([Current],0)) as CurrentAmount 
           from [cap].[FactSampledFunding] F
           WHERE F.IsDeleted = 0
           group by  FundingSourceID, FiscalYearID) AS CA on CA.FundingSourceID = FB.FundingSourceID and CA.FiscalYearID = FB.FiscalYearID

LEFT JOIN (
           IF EXISTS (SELECT FundingSourceID, FiscalYearID, SUM(COALESCE(PF.Amount,0))AS CFOApproved FROM [cap].[FactProjectFunding] PF
           INNER JOIN [cap].[DimProject] DP ON DP.ProjectID = PF.ProjectID
           INNER JOIN [dbo].[WFToken] WT ON DP.MemberGUID = WT.EntityGUID
           INNER JOIN [dbo].[WFWorkflowStep] WFT ON WFT.WorkflowStepGUID = WT.WorkflowStepGUID
           WHERE PF.IsDeleted = 0 AND WFT.Name IN ('Cancer Center Review', 'Outpatient Center Review', 'Corporate EVP CFO Review', 'Corporate EVP Review', 'Capital Committee Review')
           GROUP BY  FundingSourceID, FiscalYearID)
           SELECT FundingSourceID, FiscalYearID, SUM(COALESCE(PF.Amount,0))AS CFOApproved FROM [cap].[FactProjectFunding] PF
           INNER JOIN [cap].[DimProject] DP ON DP.ProjectID = PF.ProjectID
           INNER JOIN [dbo].[WFToken] WT ON DP.MemberGUID = WT.EntityGUID
           INNER JOIN [dbo].[WFWorkflowStep] WFT ON WFT.WorkflowStepGUID = WT.WorkflowStepGUID
           WHERE PF.IsDeleted = 0 AND WFT.Name IN ('Cancer Center Review', 'Outpatient Center Review', 'Corporate EVP CFO Review', 'Corporate EVP Review', 'Capital Committee Review')
           GROUP BY  FundingSourceID, FiscalYearID
           ELSE 
           SELECT 0 AS [FundingSourceID], 0 as [FiscalYearID], 0 as [CFOApproved]
           ) AS DE on DE.FundingSourceID = FB.FundingSourceID and DE.FiscalYearID = FB.FiscalYearID
        WHERE
         FB.FundingSourceID != 1

我得到的错误是：

Msg 156, Level 15, State 1, Line 20
Incorrect syntax near the keyword 'IF'.
Msg 102, Level 15, State 1, Line 34
Incorrect syntax near ')'.

可能是Exists语句的使用不正确，请问有没有人帮我解决一下？

Answer 1

如前所述，您不能在查询中使用 IF 语句。您正在寻找的是一种在子查询产生 NULL 结果时处理 AMOUNT 计算的方法。下面使用ISNULL表达式来处理这个问题：

SELECT
  FB.FundingSourceID,
  FB.FiscalYearID,
  ( FB.FundingBudget - ISNULL(CA.CurrentAmount, 0) - ISNULL(DE.CFOApproved, 0) ) AS Amount
FROM
  (
    SELECT
      FundingSourceID,
      FiscalYearID,
      SUM(COALESCE(Amount, 0)) AS FundingBudget
    FROM
      [cap].[FactFundingSourceBudget]
    WHERE
      IsDeleted = 0
    GROUP BY
      FundingSourceID,
      FiscalYearID
  ) AS FB
  LEFT JOIN (
              SELECT
                FundingSourceID,
                FiscalYearID,
                SUM(COALESCE([Current], 0)) AS CurrentAmount
              FROM
                [cap].[FactSampledFunding] F
              WHERE
                F.IsDeleted = 0
              GROUP BY
                FundingSourceID,
                FiscalYearID
            ) AS CA
    ON CA.FundingSourceID = FB.FundingSourceID
       AND CA.FiscalYearID = FB.FiscalYearID
  LEFT JOIN (
              SELECT
                FundingSourceID,
                FiscalYearID,
                SUM(COALESCE(PF.Amount, 0)) AS CFOApproved
              FROM
                [cap].[FactProjectFunding] PF
                INNER JOIN [cap].[DimProject] DP
                  ON DP.ProjectID = PF.ProjectID
                INNER JOIN [dbo].[WFToken] WT
                  ON DP.MemberGUID = WT.EntityGUID
                INNER JOIN [dbo].[WFWorkflowStep] WFT
                  ON WFT.WorkflowStepGUID = WT.WorkflowStepGUID
              WHERE
                PF.IsDeleted = 0
                AND WFT.Name IN ( 'Cancer Center Review',
                                  'Outpatient Center Review',
                                  'Corporate EVP CFO Review',
                                  'Corporate EVP Review',
                                  'Capital Committee Review' )
              GROUP BY
                FundingSourceID,
                FiscalYearID
            ) AS DE
    ON DE.FundingSourceID = FB.FundingSourceID
       AND DE.FiscalYearID = FB.FiscalYearID
WHERE
  FB.FundingSourceID != 1

SQL 中存在 IF 的正确用法

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