[英]MySQL query to group messages into a conversation and show the first in the inbox
例如,两个用户通过直接消息交谈,您将进行消息对话......我只想从该对话中选择最新消息,然后将其显示为他们消息收件箱中的对话链接......就像 Facebook 和 Twitter消息工作。 然后,他们可以单击最后发送的消息以查看整个对话。
我的消息表包含用户之间发送的所有消息,格式如下:
sourceUserId 是发送消息的用户的id,targetUserId 是接收消息的用户的id,body 是消息,time 是消息发送的时间戳。 我将 body 保持为 abc... 时间为 1234 以保持此示例简单,它们都是不同的值。
+----+--------------+--------------+--------+------+
| id | sourceUserId | targetUserId | body | time |
+----+--------------+--------------+--------+------+
| 1 | 1 | 2 | abc... | 1234 |
| 2 | 3 | 1 | abc... | 1234 |
| 3 | 3 | 1 | abc... | 1234 |
| 4 | 1 | 3 | abc... | 1234 |
| 5 | 2 | 1 | abc... | 1234 |
| 6 | 1 | 2 | abc... | 1234 |
| 7 | 3 | 1 | abc... | 1234 |
| 8 | 4 | 1 | abc... | 1234 |
| 9 | 5 | 4 | abc... | 1234 |
| 10 | 3 | 2 | abc... | 1234 |
+----+--------------+--------------+--------+------+
要获取一个用户的所有消息(发送和接收),我使用以下查询:
SELECT sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE targetUserId = 1
OR sourceUserId = 1
ORDER BY id DESC
LIMIT 10
+----+--------------+--------------+--------+------+
| id | sourceUserId | targetUserId | body | time |
+----+--------------+--------------+--------+------+
| 1 | 1 | 2 | abc... | 1234 |
| 2 | 3 | 1 | abc... | 1234 |
| 3 | 3 | 1 | abc... | 1234 |
| 4 | 1 | 3 | abc... | 1234 |
| 5 | 2 | 1 | abc... | 1234 |
| 6 | 1 | 2 | abc... | 1234 |
| 7 | 3 | 1 | abc... | 1234 |
| 8 | 4 | 1 | abc... | 1234 |
+----+--------------+--------------+--------+------+
但它返回同一消息对话的多个实例,而不仅仅是来自两个用户之间对话的最新消息。 例如,第 2,3 和 4 行将显示完全相同的对话。
我可以使用以下查询使查询仅适用于 targetUserId(用户收到的消息):
SELECT sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE targetUserId = 1
GROUP BY sourceUserId
ORDER BY id DESC
LIMIT 10
+----+--------------+--------------+--------+------+
| id | sourceUserId | targetUserId | body | time |
+----+--------------+--------------+--------+------+
| 2 | 3 | 1 | abc... | 1234 |
| 5 | 2 | 1 | abc... | 1234 |
| 8 | 4 | 1 | abc... | 1234 |
+----+--------------+--------------+--------+------+
与此相反(用户发送的消息),请注意 WHERE 和 GROUP BY 刚刚交换:
SELECT sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE sourceUserId = 1
GROUP BY targetUserId
ORDER BY id DESC
LIMIT 10
+----+--------------+--------------+--------+------+
| id | sourceUserId | targetUserId | body | time |
+----+--------------+--------------+--------+------+
| 1 | 1 | 2 | abc... | 1234 |
| 4 | 1 | 3 | abc... | 1234 |
+----+--------------+--------------+--------+------+
但是如果我将两个结果组合起来并按group by targetUserId, sourceUserId
那么它不会给出正确的结果,因为从 1 到 (2,3,4) 的所有传出消息都被分组。
我想返回什么
我认为这种查询的伪代码是:
SELECT sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE sourceUserId = 1
OR targetUserId = 1
GROUP BY (If targetUserId != 1), (If sourceUserId != 1)
ORDER BY id DESC
LIMIT 10
+----+--------------+--------------+--------+------+
| id | sourceUserId | targetUserId | body | time |
+----+--------------+--------------+--------+------+
| 1 | 1 | 2 | abc... | 1234 |
| 2 | 3 | 1 | abc... | 1234 |
| 8 | 4 | 1 | abc... | 1234 |
+----+--------------+--------------+--------+------+
版本 2 这是未经测试的; 它更接近但仍然不正确......虽然在这方面工作已经过时了......
SELECT Um1.sourceUserId, Um1.targetUserId, um1.body, UNIX_TIMESTAMP(um1.time)
FROM usermessages um1
WHERE um1.time =
(Select max(um1.time)
FROM usermessages um2
where um1.sourceUserID = um2.sourceUserID
and Um1.targetUserID = Um2.targetUserID,
and UM1.Body = UM2.body
and (targetuserID = 1 or sourceuserID = 1))
Group by Um1.sourceUserId, Um1.targetUserId, um1.body
ORDER BY id DESC
LIMIT 10
VERSION 1 (Miss) IMO 你也需要按身体分组。
SELECT sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE targetUserId = 1
OR sourceUserId = 1
GROUP BY sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
ORDER BY id DESC
LIMIT 10
或者使用不同的
SELECT distinct sourceUserId, targetUserId, body, UNIX_TIMESTAMP(time)
FROM `usermessages`
WHERE targetUserId = 1
OR sourceUserId = 1
ORDER BY id DESC
LIMIT 10
我认为问题真的在于那些记录的主体不同或时间戳不同; 如果没有,那么为什么它们在表中重复? 特别是在您的输出中,为什么记录 1 和 6 存在……您是否缺少一个可以防止重复的唯一索引/pk?
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