在表中找到两条具有相同值的记录

Posted 2023-03-29

【中文标题】在表中找到两条具有相同值的记录

【英文标题】：Find two records in the table that have the same value

【发布时间】：2019-07-02 12:29:18

【问题描述】：

我有一张桌子b_im_message。它有列id、chat_id、user_id。我无法创建查询，因此“user_id”列中有 3 或 4 个值，而 chat_id 列中有两个条目。很难描述。我会举个例子。

初始表格视图

mysql> select id, chat_id, user_id from b_im_relation;
+----+---------+---------+
| id | chat_id | user_id |
+----+---------+---------+
| 11 |       6 |       1 |
| 12 |       6 |       3 |
| 13 |       7 |       1 |
| 14 |       7 |       4 |
| 16 |       8 |       1 |
| 15 |       8 |       3 |
| 18 |       9 |       1 |
| 17 |       9 |       4 |
| 19 |      10 |       3 |
| 20 |      11 |       3 |
| 21 |      11 |       4 |
+----+---------+---------+
11 rows in set (0.00 sec)

选择值为 3 或 4 以及任何“chat_id”的行

mysql> SELECT id, chat_id, user_id 
       FROM b_im_relation 
       WHERE user_id IN (3,4) and  
             EXISTS(SELECT id, chat_id, user_id 
                    FROM b_im_relation t1 
                    WHERE EXISTS (SELECT 1 
                                  FROM b_im_relation t2 
                                  WHERE t1.chat_id=t2.chat_id and 
                                  t1.id<>t2.id));
+----+---------+---------+
| id | chat_id | user_id |
+----+---------+---------+
| 12 |       6 |       3 |
| 15 |       8 |       3 |
| 19 |      10 |       3 |
| 20 |      11 |       3 |
| 14 |       7 |       4 |
| 17 |       9 |       4 |
| 21 |      11 |       4 |
+----+---------+---------+
7 rows in set (0.00 sec)

选定对“chat_id”

mysql> SELECT id, chat_id, user_id 
       FROM b_im_relation t1 
       WHERE EXISTS (SELECT 1 FROM b_im_relation t2 
                     WHERE t1.chat_id=t2.chat_id and 
                              t1.id<>t2.id) and 
             EXISTS (SELECT id, chat_id, user_id 
                     FROM b_im_relation 
                     WHERE user_id in (3,4));
+----+---------+---------+
| id | chat_id | user_id |
+----+---------+---------+
| 11 |       6 |       1 |
| 12 |       6 |       3 |
| 13 |       7 |       1 |
| 14 |       7 |       4 |
| 16 |       8 |       1 |
| 15 |       8 |       3 |
| 18 |       9 |       1 |
| 17 |       9 |       4 |
| 20 |      11 |       3 |
| 21 |      11 |       4 |
+----+---------+---------+

我需要这个：

+----+---------+---------+
| id | chat_id | user_id |
+----+---------+---------+
| 20 |      11 |       3 |
| 21 |      11 |       4 |
+----+---------+---------+

任何值“id”，任何相同的值“cat_id”和“user_id”中的“3”或“4”

【参考方案1】：

如果您想要chat_ids 3 和 4 所在的 chat_ids：

select i.*
from b_im_relation i inner join (
    select chat_id
    from b_im_relation
    where user_id in (3,4)
    group by chat_id
    having count(distinct user_id) = 2
) t on t.chat_id = i.chat_id

如果您想要只有user_ids 3 和 4 的 chat_ids：

select i.*
from b_im_relation i inner join (
    select chat_id
    from b_im_relation
    group by chat_id
    having count(distinct user_id) = 2 and sum(user_id not in(3, 4)) = 0
) t on t.chat_id = i.chat_id

【讨论】：

对不起，错误 1051 (42S02): 未知表 'i'

【参考方案2】：

查找所有包含多条记录的用户/聊天组合，然后加入以获取所有此类记录：

select id, chat_id, user_id
from (
    select chat_id, user_id
    from b_im_relation
    where user_id in (3,4)
    group by chat_id, user_id
    having count(*) > 1
) multiple_chats
natural join b_im_relation