Question

我有一个我正在努力解决的MySQL查询，我似乎无法使其正常工作。

这是它的样子：

SELECT 
    DISTINCT reminders.recordID 
FROM 
    reminders, 
    (SELECT 
        DISTINCT recordID, 
        MAX(date) as MaxDate 
     FROM reminders 
     GROUP BY recordID
    ) dts 
WHERE 
    reminders.owner = '$owner'
    AND reminders.date = dts.MaxDate

我需要在表格中提醒所有提醒（提醒），例如recordID 14.然后我需要从该组结果中选择最近的日期（MAX()）并返回recordID具有最近的日期，但不超过特定日期（WHERE date <= '$date'）。

有人对我如何解决这个问题有任何想法吗？

Answer 1

怎么样......

SELECT recordID, date
FROM reminders
WHERE owner = $owner
AND date <= $date
ORDER BY date DESC
LIMIT 1

...哦，我想我现在看到：“每个ID可能会附加一些提醒”清除了一些内容。所以可能有一个更优雅的解决方案，但我猜这将工作：

    SELECT DISTINCT r1.recordID,
        (SELECT r2.date
            FROM reminders as r2
            WHERE r2.owner = $owner
            AND r2.date <= $date
            AND r2.recordID = r1.recordID
            ORDER BY r2.date DESC
            LIMIT 1) as maxDate
    FROM reminders as r1
    WHERE r1.owner = $owner
    AND r1.date <= $date

PHP MySQL从结果组中选择MAX（）

1 个答案: