在mysql中删除时间戳间隔小于5秒的重复行

Question

我有一台服务器在每次访问时向数据库添加多条记录。服务器在每次访问的2-5个记录之间完成了它。所有的数据都是相同的期望时间戳。我想每次访问只保留1条记录。并删除其他记录。

之前：

+----+----------------------+------+--------+ 
| id |  timestamp  | user | action | 
+----+----------------------+------+--------+ 
| 1 | 01-01-01-16 03:02:05 | 5 | visit | 
| 2 | 01-01-01-16 03:02:06 | 5 | visit | 
| 3 | 01-01-01-16 03:02:05 | 6 | watch | 
| 4 | 01-01-01-16 03:02:06 | 6 | watch | 
| 5 | 01-01-01-16 03:04:05 | 9 | visit | 
| 6 | 01-01-01-16 03:04:06 | 9 | visit | 
| 7 | 01-01-01-16 03:04:07 | 9 | visit | 
| 8 | 01-01-01-16 03:04:35 | 2 | see | 
+----+----------------------+------+--------+ 

预期结果：

+----+----------------------+------+--------+ 
| id |  timestamp  | user | action | 
+----+----------------------+------+--------+ 
| 1, | 01-01-01-16 03:02:05 | 5 | visit | 
| 3, | 01-01-01-16 03:02:05 | 6 | watch | 
| 4, | 01-01-01-16 03:02:06 | 6 | watch | 
| 5, | 01-01-01-16 03:04:05 | 9 | visit | 
| 8, | 01-01-01-16 03:04:35 | 2 | see | 
+----+----------------------+------+--------+ 

换句话说：正如所看到的，线1,2是相同的。同一个用户，并且只有一秒之间。所以我删除线2.4，我不碰线，因为它不是一个访问

我有查询的开头：delete from table where id in(...)

Answer 1

使用join执行查询更快

DELETE t1 FROM visit t1 
INNER JOIN visit t2 ON v1.user = v2.user 
WHERE v1.id < v2.id AND 
TIMESTAMPDIFF(SECOND, t1.timestamp, t2.timestamp) < 5 AND 
t1.action = 'visit' AND 
t2.action = 'visit' 

Answer 2

DELETE FROM visit 
     WHERE id IN (
       SELECT v2.id 
       FROM visit v1   
       JOIN visit v2 
       ON v1.id < v2.id 
       AND v1.user = v2.user      
       AND TIMESTAMPDIFF(SECOND, v1.timestamp, v2.timestamp) < 5 
       WHERE v1.action = 'visit'   
       AND v2.action = 'visit'        
       )