mysql - 多个左连接影响了我的 SUM(TIMESTAMPDIFF 计算

Question

我目前正在尝试为上周我的 PHPBB3 论坛上的一些人预订的总时间创建一个报告。最初，我有以下查询按预期工作：

SELECT forum_users.username, SUM(TIMESTAMPDIFF(SECOND, schedule_slots.time_starting, schedule_slots.time_finishing)) AS seconds 
FROM forum_users 
LEFT JOIN schedule_slots 
    ON forum_users.user_id = schedule_slots.user_id 
    AND schedule_slots.time_starting >= (CURDATE() - INTERVAL 1 WEEK) 
    AND schedule_slots.is_del = 0 
    AND schedule_slots.channel = 0
WHERE (forum_users.group_id = 8 OR forum_users.group_id = 5 OR forum_users.group_id = 14) 
GROUP BY forum_users.username 
ORDER BY upper(forum_users.username)

但是，当我去加入另一个表时，时间戳差异最终被错误地计算（它更高），这是我较新的非工作语句：

SELECT forum_users.username, SUM(TIMESTAMPDIFF(SECOND, schedule_slots.time_starting, schedule_slots.time_finishing)) AS seconds, group_concat(DISTINCT forum_user_group.group_id) AS user_groups 
FROM forum_users 
LEFT JOIN schedule_slots 
    ON forum_users.user_id = schedule_slots.user_id 
    AND schedule_slots.time_starting >= (CURDATE() - INTERVAL 1 WEEK) 
    AND schedule_slots.is_del = 0 
    AND schedule_slots.channel = 0 
LEFT JOIN forum_user_group 
    ON forum_user_group.user_id = forum_users.user_id 
WHERE (forum_users.group_id = 8 OR forum_users.group_id = 5 OR forum_users.group_id = 14 OR forum_users.group_id = 12) 
GROUP BY forum_users.username 
ORDER BY upper(forum_users.username)

我在这个上画了一个空白，非常感谢您的帮助。

Answer 1

时间戳差异是正确计算的，但是您将其乘以用户所在的组数。

我会尝试：

SELECT forum_users.username, SUM(TIMESTAMPDIFF(SECOND, schedule_slots.time_starting, schedule_slots.time_finishing)) AS seconds, 
(select group_concat(DISTINCT group_id) from forum_user_group WHERE forum_user_group.user_id = forum_users.user_id) AS user_groups 
FROM forum_users 
LEFT JOIN schedule_slots 
ON forum_users.user_id = schedule_slots.user_id 
AND schedule_slots.time_starting >= (CURDATE() - INTERVAL 1 WEEK) 
AND schedule_slots.is_del = 0 
AND schedule_slots.channel = 0 
WHERE (forum_users.group_id = 8 OR forum_users.group_id = 5 OR forum_users.group_id = 14 OR forum_users.group_id = 12) 
GROUP BY forum_users.username, user_groups 
ORDER BY upper(forum_users.username)