SQL CASE 检查同一列中的两个条件

Question

我目前有一个 CASE 语句，用于检查某些任务是否已完成，然后返回下一个任务的日期。由于任务是有序的，每个 WHEN 语句都会变长，检查之前的每个任务以查看它们是否完成。出于某种原因，在第一个 WHEN 语句之后，它直接跳到 ELSE(它应该满足第二个或第三个 WHEN 的条件)。

CASE
    WHEN T.PRNAME = 'TECH PEP MEETING DATE' AND T.PRSTATUS != 2 THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'TECH PEP MEETING DATE' AND PRISMILESTONE = 1)
    WHEN (T.PRNAME = 'TECH PEP MEETING DATE' AND T.PRSTATUS = 2) AND (T.PRNAME = 'BRU MEETING DATE' AND T.PRSTATUS != 2) THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'BRU MEETING DATE' AND PRISMILESTONE = 1)
    WHEN (T.PRNAME = 'TECH PEP MEETING DATE' AND T.PRSTATUS = 2) AND (T.PRNAME = 'BRU MEETING DATE' AND T.PRSTATUS = 2) AND (T.PRNAME = 'TSC MEETING DATE' AND T.PRSTATUS != 2) THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'TSC MEETING DATE' AND PRISMILESTONE = 1) 
    ELSE (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'END OF EVALUATE PHASE' AND PRISMILESTONE = 1)
END

您是否需要一种特定的方法来解决这些类型的多个 WHEN 条件？

编辑:所以在得到你们的一些反馈后，我同意你只需要在每个 WHEN 评估一个任务的想法，因为 CASE 语句一旦找到它的第一个 TRUE 语句就应该退出。但是，已将其更新为:

CASE
    WHEN UPPER(T.PRNAME) = 'EVALUATE TECH PEP MEETING DATE' AND T.PRSTATUS != 2 THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'TECH PEP MEETING DATE' AND PRISMILESTONE = 1 AND ROWNUM = 1)
    WHEN UPPER(T.PRNAME) = 'EVALUATE BRU MEETING DATE' AND T.PRSTATUS != 2 THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'BRU MEETING DATE' AND PRISMILESTONE = 1 AND ROWNUM = 1)
    WHEN UPPER(T.PRNAME) = 'EVALUATE TSC MEETING DATE' AND T.PRSTATUS != 2 THEN (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'TSC MEETING DATE' AND PRISMILESTONE = 1 AND ROWNUM = 1) 
    ELSE (SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') FROM PRTASK T WHERE T.PRPROJECTID = INV_INVESTMENTS.ID AND Upper(T.PRNAME) = 'END OF EVALUATE PHASE' AND PRISMILESTONE = 1)
END

我现在得到:

ORA-01427: single-row subquery returns more than one row

不知道为什么会这样，尤其是放置了 ROWNUM = 1最后确保只返回一个结果。

单独运行 THEN 时:

SELECT TO_CHAR(MAX(T.PRFINISH),'DD/MM/YY') 
FROM PRTASK T 
WHERE T.PRPROJECTID = INV_INVESTMENTS.ID 
AND Upper(T.PRNAME) = 'TECH PEP MEETING DATE' 
AND PRISMILESTONE = 1 
AND ROWNUM = 1

我得到一个结果。如果我认为 CASE 语句一旦找到它的第一个 TRUE 语句就会退出是正确的，那么为什么会发现多行？

编辑 2:好的 - 所以我一直在玩这个(因为我仍然找不到合乎逻辑的答案并且我已经取得了一些进展。我现在已经改变了查询的结构方式如下:

SELECT DISTINCT To_Char(T.PRFINISH, 'DD/MM/YY'),
                T.PRNAME  
FROM  PRTASK T
      LEFT OUTER JOIN INV_INVESTMENTS ON T.PRPROJECTID = INV_INVESTMENTS.ID
WHERE T.PRNAME = CASE 
                     WHEN (T.PRNAME = 'Concept Tech PEP Meeting Date' AND T.PRSTATUS != 2) THEN 'Concept Tech PEP Meeting Date'
                     WHEN (T.PRNAME = 'Concept BRU Meeting Date' AND T.PRSTATUS != 2) THEN 'Concept BRU Meeting Date'
                     WHEN (T.PRNAME = 'End of Concept Phase' AND T.PRSTATUS != 2) THEN 'End of Concept Phase'                                                                                                                
                     WHEN (T.PRNAME = 'Evaluate Tech PEP Meeting Date' AND T.PRSTATUS != 2) THEN 'Evaluate Tech PEP Meeting Date'
                     WHEN (T.PRNAME = 'Evaluate BRU Meeting Date' AND T.PRSTATUS != 2) THEN 'Evaluate BRU Meeting Date'
                     WHEN (T.PRNAME = 'Evaluate TSC Meeting Date' AND T.PRSTATUS != 2) THEN 'Evaluate TSC Meeting Date'
                     WHEN (T.PRNAME = 'End of Evaluate Phase' AND T.PRSTATUS != 2) THEN 'End of Evaluate Phase'                      
                     WHEN (T.PRNAME = 'End of Analyse Phase' AND T.PRSTATUS != 2) THEN 'End of Analyse Phase'
                     WHEN (T.PRNAME = 'End of Design Phase' AND T.PRSTATUS != 2) THEN 'End of Design Phase'
                     WHEN (T.PRNAME = 'End of Build Phase' AND T.PRSTATUS != 2) THEN 'End of Build Phase'
                     WHEN (T.PRNAME = 'End of Test Phase' AND T.PRSTATUS != 2) THEN 'End of Test Phase'
                     WHEN (T.PRNAME = 'In Service' AND T.PRSTATUS != 2) THEN 'In Service'                    
                     WHEN (T.PRNAME = 'End of Implement Phase' AND T.PRSTATUS != 2) THEN 'End of Implement Phase'  
                     WHEN (T.PRNAME = 'End of Closure Phase' AND T.PRSTATUS != 2) THEN 'End of Closure Phase'
                     ELSE 'In Service'
                  END
     AND INV_INVESTMENTS.CODE = '007058'

但是，现在我收到多个返回值的 WHEN 语句。谁能确认 CASE 语句是否真的只返回第一个 TRUE 值？

Answer 1

T.PRNAME = 'TECH PEP session 日期' 和 T.PRNAME = 'BRU session 日期'？我认为我们在这里遇到了重叠的情况。

我在这里的高度假设是，您有 1 张表，旁边有许多带有状态的任务，那么我认为这里应该发生的事情如下所示。

首先是你的任务表，我自己创建了一些东西。

CREATE TABLE #testtask
  (
    PRID INT
    , PRNAME varchar(50)
    , PRSTATUS INT
    , PREREQ INT
  )

  INSERT INTO #testtask VALUES
  (1,'TECH PEP MEETING DATE',1,0),
  (2,'BRU MEETING DATE',1,1),
  (3,'TSC MEETING DATE',1,2)

可能是这样的



然后，我在它自己的表上创建了一个与其先决任务相关的左联接。

SELECT
     t1.PRNAME AS [Job]
     , t1.PRSTATUS AS [JobStatus]
     , t2.PRNAME AS [PreReqJob]
     , t2.PRSTATUS AS [PreReqStatus]
  INTO #taskList
  FROM #testtask t1
  LEFT JOIN #testtask t2
  ON
    t1.PREREQ = t2.PRID

并得到以下结果。



在进入我认为是您的脚本检查每个任务状态与先决任务之前。

SELECT
      CASE
        WHEN tl.[Job] = 'TECH PEP MEETING DATE' AND tl.[JobStatus] != 2
            THEN
                -- do your max select here for 'Tech pep'
        WHEN tl.[Job] = 'BRU MEETING DATE' AND tl.[JobStatus] != 2 AND tl.[PreReqStatus] = 2
            THEN
                -- do your max select here for 'Bru meet'
        WHEN tl.[Job] = 'TSC MEETING DATE' AND tl.[JobStatus] != 2 AND tl.[PreReqStatus] = 2
            THEN
                -- do your max select here for 'Tsc meet'
        ELSE
            -- do your default max date
     END AS [Date]
  FROM #taskList AS tl

请单独了解这个概念，因为我没有您的实际表格。如果您复制整个内容，您几乎会出错。希望这会有所帮助:)