Question

先谢谢，我使用的是oracle 10g。在SQL case语句中，我们传递值并根据值和返回字符串检查大小写。但我没有返回String，而是想返回一个表达式。这是否可以使用oracle SQL查询CASE语句返回表达式？我执行以下操作，oracle生成错误ORA-00905:Missing Keyword

SELECT ECL_CONTROL,
  CASE 
    WHEN ECL_CONTROL = 'N' THEN ('##0') = ('##0')
    WHEN ECL_CONTROL = 'Y' THEN (NVL(IL.ECL, 'X') = NVL(IM.ECL, 'X'))
  END
FROM ITEM_CONTROL WHERE ITEM_NO =  '2N2907A'

但以下成功运行：

SELECT ECL_CONTROL,
  CASE 
    WHEN ECL_CONTROL = 'N' THEN 'test'
    WHEN ECL_CONTROL = 'Y' THEN 'demo'
  END
FROM ITEM_CONTROL WHERE ITEM_NO =  '2N2907A'

我想将此查询用作内部查询以及外部查询的返回和表达式。我的查询如下：

SELECT  LSM.ACTIVE_FLAG, LSM.ITEM_NO, IL.ECL, LSM.SERIAL_NO, IL.WAREHOUSE, IL.BIN, LSM.TOOL_STATUS_CODE,
LLG.NEXT_CAL_DATE, IM.PRODUCT_GROUP
FROM LS_SERIAL_MASTER LSM, LS_LIFE_LOG LLG, ITEM_LOCATION IL, ITEM_MASTER IM
WHERE   IL.PLANT = IM.PLANT AND IL.ITEM_NO = IM.ITEM_NO 
AND IM.PLANT = LSM.PLANT AND IM.ITEM_NO = LSM.ITEM_NO AND NVL(IM.PRODUCT_GROUP, 'X') =    NVL('PUMP', 'X')
AND LSM.PLANT = LLG.PLANT AND LSM.ITEM_NO = LLG.ITEM_NO AND LSM.SERIAL_NO = LLG.SERIAL_NO
AND LSM.LIFE_TRANS_ID = LLG.TRANS_ID AND LLG.SERIAL_NO = IL.SERIAL_NO
AND (SELECT ECL_CONTROL,
  CASE ECL_CONTROL
    WHEN ECL_CONTROL = 'N' THEN ('##0' = '##0')
    WHEN ECL_CONTROL = 'Y' THEN (NVL(IL.ECL, 'X') = NVL(IM.ECL, 'X'))
  END AS ECL_CONTROL_TXT
  FROM ITEM_CONTROL WHERE ITEM_NO =  '2N2907A')
AND LLG.MAINT_LMT_ID IN('T', 'U')
AND LLG.NEXT_CAL_DATE BETWEEN TO_DATE('02/1/2014', 'MM/DD/YYYY') AND TO_DATE('02/11/2014', 'MM/DD/YYYY').

我的实际任务是从内部查询返回一个表达式并在外部查询中使用。

Answer 1

不，你所展示的是不可能的。真正在select中使用表达式是没有意义的。你可以have an expression evaluated instead of using a fixed string：

SELECT ECL_CONTROL,
  CASE 
    WHEN ECL_CONTROL = 'N' THEN '##0'
    WHEN ECL_CONTROL = 'Y' THEN NVL(IL.ECL, 'X')
  END
FROM ITEM_CONTROL WHERE ITEM_NO =  '2N2907A'

但你无法返回实际的表达方式。在您已经显示的代码中，第一个表达式总是会评估为true（并且普通SQL中也不存在布尔值），所以我认为这可能是您实际想要的并且您对如何分配表达式值。您尚未显示IL和IM的来源，因此很难说出您想要的内容。

您可以直接在case子句中使用where：

SELECT ...
FROM IM, IL, ITEM_CONTROL -- joined in some way
WHERE CASE 
    WHEN ECL_CONTROL = 'N' THEN '##0'
    WHEN ECL_CONTROL = 'Y' THEN NVL(IL.ECL, 'X')
  END = CASE 
    WHEN ECL_CONTROL = 'N' THEN '##0'
    WHEN ECL_CONTROL = 'Y' THEN NVL(IM.ECL, 'X')
  END

虽然这可能更清楚：

WHERE ECL_CONTROL = 'N' OR NVL(IL.ECL, 'X') = NVL(IM.ECL, 'X')

您添加的较大查询：

SELECT LSM.ACTIVE_FLAG, LSM.ITEM_NO, IL.ECL, LSM.SERIAL_NO, IL.WAREHOUSE,
  IL.BIN, LSM.TOOL_STATUS_CODE, LLG.NEXT_CAL_DATE, IM.PRODUCT_GROUP
FROM LS_SERIAL_MASTER LSM, LS_LIFE_LOG LLG, ITEM_LOCATION IL, ITEM_MASTER IM
WHERE IL.PLANT = IM.PLANT AND IL.ITEM_NO = IM.ITEM_NO 
AND IM.PLANT = LSM.PLANT AND IM.ITEM_NO = LSM.ITEM_NO
AND NVL(IM.PRODUCT_GROUP, 'X') = NVL('PUMP', 'X')
AND LSM.PLANT = LLG.PLANT AND LSM.ITEM_NO = LLG.ITEM_NO
AND LSM.SERIAL_NO = LLG.SERIAL_NO
AND LSM.LIFE_TRANS_ID = LLG.TRANS_ID AND LLG.SERIAL_NO = IL.SERIAL_NO
AND LLG.MAINT_LMT_ID IN('T', 'U')
AND LLG.NEXT_CAL_DATE BETWEEN TO_DATE('02/1/2014', 'MM/DD/YYYY')
  AND TO_DATE('02/11/2014', 'MM/DD/YYYY')
AND ((SELECT ECL_CONTROL FROM ITEM_CONTROL WHERE ITEM_NO = '2N2907A') = 'N'
  OR NVL(IL.ECL, 'X') = NVL(IM.ECL, 'X'))

...虽然因为子查询正在寻找一行 - 具有固定的item_no，它与您在其他表中引用的同名的其他列有关 - 您可以将该表包含在其中主要查询。

无论哪种方式。顺便提一下，明确连接会更清楚;而不是问题的范围，但接受你的评论，item_no实际上是相关的，如：

SELECT LSM.ACTIVE_FLAG, LSM.ITEM_NO, IL.ECL, LSM.SERIAL_NO, IL.WAREHOUSE,
  IL.BIN, LSM.TOOL_STATUS_CODE, LLG.NEXT_CAL_DATE, IM.PRODUCT_GROUP
FROM LS_LIFE_LOG LLG
JOIN LS_SERIAL_MASTER LSM ON LSM.PLANT = LLG.PLANT
  AND LSM.ITEM_NO = LLG.ITEM_NO
  AND LSM.SERIAL_NO = LLG.SERIAL_NO
  AND LSM.LIFE_TRANS_ID = LLG.TRANS_ID
JOIN ITEM_CONTROL IC ON IC.ITEM_NO = LSM.ITEM_NO
JOIN ITEM_MASTER IM ON IM.PLANT = LSM.PLANT
  AND IM.ITEM_NO = IC.ITEM_NO
JOIN ITEM_LOCATION IL ON IL.PLANT = IM.PLANT
  AND IL.ITEM_NO = IM.ITEM_NO
  AND IL.SERIAL_NO = LLG.SERIAL_NO
  AND (IC.ECL_CONTROL = 'N' OR NVL(IL.ECL, 'X') = NVL(IM.ECL, 'X'))
WHERE LLG.MAINT_LMT_ID IN ('T', 'U')
AND LLG.NEXT_CAL_DATE BETWEEN TO_DATE('02/1/2014', 'MM/DD/YYYY')
  AND TO_DATE('02/11/2014', 'MM/DD/YYYY')
AND NVL(IM.PRODUCT_GROUP, 'X') = NVL('PUMP', 'X')

NVL('PUMP', 'X')没有意义 - NVL()在固定值附近毫无意义。也许代替AND NVL(IM.PRODUCT_GROUP, 'X') = NVL('PUMP', 'X')而不是AND (IM.PRODUCT_GROUP IS NULL OR IM.PRODUCT_GROUP = 'PUMP')？

SQL：从SQL CASE语句返回表达式

1 个答案: