Question

如何获取按最大列排序并按ID分组的行列表？我不断获得正确的最大值，但其他字段是从其他行获得的。

我使用以下内容：

SELECT p.*
            FROM `logs` AS p
            JOIN
            (SELECT person_id,
             MAX(`datetime`) AS datetime
             FROM `logs`
             GROUP BY `person_id`
             ) AS pg
             ON  pg.person_id = p.person_id
             AND pg.`datetime` = p.datetime
             group by person_id

我的查询在哪里错了？日期时间和人员ID始终是正确的，但其他字段不是。

Answer 1

请参阅：http://bugs.mysql.com/bug.php?id=54784

Answer 2

SELECT MIN（datetime）并不总是返回最小日期时间值。与MAX相同。

临时解决方法：

        SELECT p.*
        FROM   `logs` AS p
        JOIN
              (SELECT person_id,
                      MAX(CAST(`datetime` as CHAR(25))) AS `datetime`
               FROM `logs`
               GROUP BY `person_id`
               ) AS pg
                   ON  pg.person_id = p.person_id AND
              pg.`datetime` = p.datetime
         group by person_id

Answer 3

请尝试以下方法：

SELECT logs.* 
  FROM ( SELECT person_id,
             MAX(`datetime`) AS latest
             FROM `logs` 
         GROUP BY person_id) AS dt
INNER
  JOIN logs 
    ON logs.person_id= dt.person_id
   AND logs.datetime= dt.latest

MySQL：MAX没有返回

3 个答案: