Mysql的基础上添加条件

Question

时候我已经一个表，它的结构是这样如下

+---------------------+---------+ 
| date_time   | portNo1 | 
+---------------------+---------+ 
| 2016-01-08 13:15:46 |  1 | 
| 2016-01-08 13:16:01 |  2 | 
| 2016-01-08 13:16:16 |  1 | 
| 2016-01-08 13:16:31 |  2 | 
| 2016-01-08 13:16:46 |  1 | 
| 2016-01-08 13:17:00 |  2 | 
| 2016-01-08 13:17:16 |  1 | 
| 2016-01-08 13:17:31 |  1 | 
| 2016-01-08 13:17:46 |  0 | 
| 2016-01-08 13:18:01 |  0 | 
| 2016-01-08 13:18:16 |  0 | 
| 2016-01-08 13:18:31 |  0 | 
| 2016-01-08 13:18:41 |  0 | 
| 2016-01-08 13:19:01 |  0 | 
| 2016-01-08 13:19:16 |  0 | 
| 2016-01-08 13:19:27 |  0 | 
| 2016-01-08 13:19:41 |  0 | 
| 2016-01-08 13:19:56 |  0 | 
| 2016-01-08 13:20:11 |  0 | 
| 2016-01-08 13:20:26 |  0 | 
| 2016-01-08 13:20:41 |  0 | 
| 2016-01-08 13:20:56 |  0 | 
| 2016-01-08 13:21:16 |  0 | 
| 2016-01-08 13:21:31 |  0 | 
| 2016-01-08 13:21:43 |  0 | 
| 2016-01-08 13:22:01 |  0 | 
| 2016-01-08 13:22:16 |  0 | 
| 2016-01-08 13:22:31 |  0 | 
| 2016-01-08 13:22:46 |  0 | 
| 2016-01-08 13:23:01 |  0 | 
| 2016-01-08 13:23:12 |  0 | 
| 2016-01-08 13:23:31 |  0 | 
| 2016-01-08 13:23:46 |  2 | 
| 2016-01-08 13:24:01 |  2 | 
| 2016-01-08 13:24:16 |  2 | 
| 2016-01-08 13:24:31 |  1 | 
| 2016-01-08 13:24:46 |  2 | 
| 2016-01-08 13:25:00 |  2 | 

现在我要做的就是只会增加其portNo1值的时间不是0 这意味着它应该添加时间从13:15:46到13:17:31以秒为单位，那么自此之后所有记录到13:23:46的值是0它应该忽略该时间并继续。那么从13:23:46再次有portNo1值它应该采取差异13:23:46和13:23:31并将其添加到以前的差异。如果在mysql中有任何简单的方法，请告诉我，我在Perl中尝试了很多，但没有得到正确的值。

Answer 1

除非我理解题目都错了，你可以这样做：

SELECT SUM(UNIX_TIMESTAMP(date_time)-UNIX_TIMESTAMP(prevtime)) 
FROM (
    SELECT date_time, portNo1, @prevTime as prevtime, 
    @prevTime := date_time 
    FROM MyTable 
) t1 
WHERE (portNo1 > 0 AND prevtime IS NOT null) 

这将在总结当前行与前一行之间的时间差（以秒为单位），如果portNo1当前行大于0.这是你想要的吗？

我做了这里提琴：http://sqlfiddle.com/#!9/b6dfa/3