MySQL：行之间的时间

Question

我是MySQL的新手，我正在试图弄清楚如何计算日志表中各行之间的时间。

该表是一个基本表，包含ID，主机名，信息，时间戳，数据如：

+---+----------+-------------------+---------------------+
|ID | Hostname | Info              | Timestamp           |
+---+----------+-------------------+---------------------+
|445| switch1  | "port 1 inserted" | 2013-01-19 19:51:40 |
|446| switch1  | "port 2 inserted" | 2013-01-19 19:59:41 |
|447| Router2  | "alarm fan speed" | 2013-01-19 20:00:40 |
|448| switch1  | "alarm fan speed" | 2013-01-19 20:12:20 |
|449| Router2  | "alarm fan speed" | 2013-01-19 21:42:41 |
+---+----------+-------------------+---------------------+

所以基本上我想得到具有相同HOSTNAME的行之间的时差，在这种情况下，在行445和446之间它将导致8分1秒。在446和448之间，它将导致12分39秒。等等...

对此有任何提示将不胜感激。

Answer 1

这将为您提供行之间的时间差异：

SELECT c.info, 
       CASE 
         WHEN f.`timestamp` IS NOT NULL THEN 
         Timestampdiff(second, f.`timestamp`, 
         c.`timestamp`) 
         ELSE NULL 
       end AS time_diff 
FROM   (SELECT @rowa := @rowa + 1 AS id, 
               a.hostname, 
               a.info, 
               a.`timestamp` 
        FROM   sparkles a 
               JOIN (SELECT @rowa := 0) b 
        WHERE  a.hostname = 'switch1') c 
       LEFT JOIN (SELECT @rowb := @rowb + 1 AS id, 
                         d.hostname, 
                         d.info, 
                         d.`timestamp` 
                  FROM   sparkles d 
                         JOIN (SELECT @rowb := 0) e 
                  WHERE  d.hostname = 'switch1') f 
              ON f.id = c.id - 1 

结果（对于 switch1 作为hostname）

|            INFO | TIME_DIFF |
-------------------------------
| port 1 inserted |    (null) |
| port 2 inserted |       481 |
| alarm fan speed |       759 |

See the demo

结果（对于 Router2 作为hostname）

|            INFO | TIME_DIFF |
-------------------------------
| alarm fan speed |    (null) |
| alarm fan speed |      6121 |

See the demo

Answer 2

试试这个：

SELECT id, IF(@lastdate = '', NULL, TIMESTAMPDIFF(SECOND, TIMESTAMP, @lastdate)), 
       @lastdate:=TIMESTAMP 
FROM tablename, (SELECT @lastdate:='') a;