php-从数据库查找最小日期

我有如下查询：

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条件无法正常运行,并且MIN日期不符合我的预期.

我期望上面的记录,但是它返回表中前一张图像的第一条记录：

解决方法:

由于聚合函数MIN()会忽略NULL值,因此您可以尝试从ActualTriggerDateTime列中选择最小日期,在特殊情况下,此列上的所有值均为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