最短日期從數據庫中查找

Question

我有一個查詢如下：

SELECT
    IsTestBatch,
    BatchID,
    CampaignID,
    IF(ActualTriggerDateTime IS NOT NULL,
       MIN(ActualTriggerDateTime),
       MIN(TriggerDateTime)) AS NextQueuedOn
FROM
    campaignbatches
WHERE
    Status IN (2,3)
GROUP BY
    CampaignID
ORDER BY
    IF(ActualTriggerDateTime IS NOT NULL, ActualTriggerDateTime, TriggerDateTime) ASC

if條件不能正常工作，並且MIN日期不正確，正如我所料。

我期待上面的記錄，但它返回上一張圖片的表中的第一條記錄：

Answer 1

由於聚合函數MIN()忽略NULL值，您可以嘗試從ActualTriggerDateTime列中選擇最小日期，並且在特殊情況下，此列上的所有值都為NULL，然后從TriggerDateTime列中選擇最小值。

SELECT
    IsTestBatch,
    BatchID,
    CampaignID,
    IFNULL(MIN(ActualTriggerDateTime), MIN(TriggerDateTime)) AS NextQueuedOn
FROM
    campaignbatches
WHERE
    Status IN (2,3)
GROUP BY
    IsTestBatch, BatchID, CampaignID
ORDER BY
    NextQueuedOn ASC

Answer 2

所有選擇列都將分組

SELECT IsTestBatch,BatchID,CampaignID,
 coalesce(MIN(ActualTriggerDateTime),MIN(TriggerDateTime)) AS NextQueuedOn 
 FROM campaignbatches
WHERE Status IN (2,3)
   and IsTestBatch=1 and BatchID=42 -- as you want single row
 GROUP BY IsTestBatch,BatchID,
   CampaignID 
ORDER BY NextQueuedOn ASC