最短日期从数据库中查找

Question

我有一个查询如下：

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条件不能正常工作，并且MIN日期不正确，正如我所料。

我期待上面的记录，但它返回上一张图片的表中的第一条记录：

Answer 1

由于聚合函数MIN()忽略NULL值，您可以尝试从ActualTriggerDateTime列中选择最小日期，并且在特殊情况下，此列上的所有值都为NULL，然后从TriggerDateTime列中选择最小值。

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

所有选择列都将分组

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