Mysql 如何根据用户的第一个条目更新字段?
我有一个表名设备Mysql 如何根据用户的第一个条目更新字段?,mysql,sql-update,Mysql,Sql Update,我有一个表名设备 +---------+---------------+---------------------+ | user_id | device_status | created_at | +---------+---------------+---------------------+ | 1 | 0 | 2017-03-10 10:39:41 | | 1 | 0 | 2017-03-14 10
+---------+---------------+---------------------+
| user_id | device_status | created_at |
+---------+---------------+---------------------+
| 1 | 0 | 2017-03-10 10:39:41 |
| 1 | 0 | 2017-03-14 10:19:33 |
| 2 | 0 | 2017-03-14 10:57:59 |
| 1 | 0 | 2017-03-15 05:58:51 |
| 3 | 0 | 2017-03-15 06:01:32 |
| 3 | 0 | 2017-03-15 12:10:13 |
+---------+---------------+---------------------+
我想做的是更新首先存储在mysql表中的用户id的device\u status
例如,我们有3行用户_id 1。在日期处创建了_。我想更新在2017-03-10 10:39:41创建的用户_id 1的设备_状态
编辑1:我使用的查询
UPDATE devices
SET device_status = 1
WHERE created_at = (SELECT created_at
FROM (SELECT MIN(created_at) AS created_at
FROM devices) AS t);
但该查询只更新了一条记录(2017-03-10 10:39:41)。
我想更新一下
| 2 | 0 | 2017-03-14 10:57:59 |
及
也要记录。在带有where子句的子查询中使用min()函数
update devices set device_status=1 where user_id = 1 and
created_at = (select min(created_at) where user_id = 1);
希望它能解决您的问题。如果您所有的日期都是互斥的,您可以根据用户id进行分组:
UPDATE devices
SET device_status = 1
WHERE created_at IN (SELECT created_at
FROM (SELECT MIN(created_at) AS created_at
FROM devices
GROUP BY user_id) AS t);
您是否尝试过使用min(创建于)??您面临哪些问题?问题是如何检查用户id?您希望每次都进行批更新还是单行更新?发布
SQL
tried@RealCheeseLord等等,让我来编辑这篇文章。
UPDATE devices
SET device_status = 1
WHERE created_at IN (SELECT created_at
FROM (SELECT MIN(created_at) AS created_at
FROM devices
GROUP BY user_id) AS t);