如何根據用戶的第一個條目更新字段？

Question

我有一個表名稱設備。

+---------+---------------+---------------------+ 
| 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 | 
+---------+---------------+---------------------+ 

我想要做的是首先已經存儲在MySQL表爲user_id的更新device_status。

例如我們有3行user_id 1和created_at date。我想更新user_id 1的device_status created_at日期2017-03-10 10:39:41。

編輯1：查詢我使用

UPDATE devices 
    SET device_status = 1 
WHERE created_at = (SELECT created_at 
         FROM (SELECT MIN(created_at) AS created_at 
           FROM devices) AS t); 

但這查詢只更新一條記錄（2017年3月10日10:39:41）。 我想更新

|  2 |    0 | 2017-03-14 10:57:59 | 

和

|  3 |    0 | 2017-03-15 06:01:32 | 

記錄了。

Answer 1

如果你的日期是互相排斥的你可以只通過組USER_ID：

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); 

Answer 2

在帶有where子句的子查詢中使用min（）函數。

update devices set device_status=1 where user_id = 1 and 
created_at = (select min(created_at) where user_id = 1); 

希望它能解決您的問題。