Mysql 使用不同的
我有两张表，Mysql 使用不同的,mysql,Mysql,我有两张表，follow和following 跟随 +---------+----------------+ | user_id | follow_user_id | +---------+----------------+ | 1 | 2 | | 2 | 3 | | 3 | 4 | | 100 | 10 | +---------+----------
followfollowing+---------+----------------+
| user_id | follow_user_id |
+---------+----------------+
| 1 | 2 |
| 2 | 3 |
| 3 | 4 |
| 100 | 10 |
+---------+----------------+
+---------+-------------------+
| user_id | following_user_id |
+---------+-------------------+
| 1 | 2 |
| 3 | 4 |
| 4 | 6 |
| 200 | 500 |
+---------+-------------------+
+---------+----------------+-----------+
| user_id | target_user_id | category |
+---------+----------------+-----------+
| 1 | 2 | follow |
| 2 | 3 | follow |
| 3 | 4 | follow |
| 4 | 6 | following |
| 100 | 10 | follow |
| 200 | 500 | following |
+---------+----------------+-----------+
followfollow跟随用户id目标用户id跟随用户id目标用户id谢谢 只需使用
uniongroupbyselect
user_id,target_user_id,min(tag) as category
from
(
select user_id,follow_user_id as target_user_id, 'follow' as tag from follow
union
select user_id,following_user_id as target_user_id, 'following' as tag from following
) tmp
group by
user_id,target_user_id
order by
user_id,target_user_id;
+---------+----------------+-----------+
| user_id | target_user_id | category |
+---------+----------------+-----------+
| 1 | 2 | follow |
| 2 | 3 | follow |
| 3 | 4 | follow |
| 4 | 6 | following |
| 100 | 10 | follow |
| 200 | 500 | following |
+---------+----------------+-----------+
6 rows in set (0.00 sec)
“条件3-如果类别重复，它可以是follow或follow。这没关系。”如果follow和follow在这里的意思差不多，为什么有两个表？理想情况下，您应该制作一个表
eventevent\u type\u idfollowfollowevent\u typefollow_idfollow_idtarget\u user\u idfollowing\u user\u idfollowing\u user\u id