I have table [visit]. I need to get the rows grouped by user\_id with sum of visit\_duration\_seconds for when order\_number is null, for example, for user [2875636] i'll get: 61+151+33+13. Each row should include the sum of the rows before it.  

Plz also refer RESULT column in expected result below 

> 
> 
> ```
> user_id   starttime           visit_duration_seconds  order_number
> 2875636   2013-01-16 18:03:50 61  
> 2875636   2013-01-16 18:08:18 151 
> 2875636   2013-01-16 18:15:43 33  
> 2875636   2013-01-16 18:16:37 13  
> 2875636   2013-01-16 18:18:01 2011                     10177888
> 2875636   2013-01-16 18:24:35 1172                     10177884
> 2875636   2013-01-16 18:32:03 4731    
> 2875636   2013-01-16 18:33:27 407 
> 2875636   2013-01-16 18:37:29 74  
> 2875636   2013-01-16 18:48:55 80  
> 2875636   2013-01-16 19:05:00 1955    
> 2875636   2013-01-16 19:14:12 326 
> 2875636   2013-01-16 19:23:39 972 
> 2875636   2013-01-16 19:33:05 5440    
> 2875636   2013-01-16 19:35:48 43  
> 2875636   2013-01-16 19:41:10 66  
> 2875636   2013-01-16 19:42:03 100 
> 2875636   2013-01-16 19:42:12 2414                     10177940
> 2875636   2013-01-16 19:49:05 432                  10177925
> 2875636   2013-01-16 19:50:19 183 
> 2875636   2013-01-16 19:52:46 2061    
> 2875636   2013-01-16 19:52:53 400 
> 2875636   2013-01-16 20:00:47 338 
> 2875636   2013-01-16 20:08:58 216 
> 2875636   2013-01-16 20:14:21 58  
> 2875636   2013-01-16 20:14:26 196 
> 2875636   2013-01-16 20:19:14 2189    
> 2875636   2013-01-16 20:21:29 424 
> 2875636   2013-01-16 20:24:42 999 
> 2875636   2013-01-16 21:01:39 1810    
> 2875636   2013-01-16 21:02:54 525 
> 2875636   2013-01-16 21:10:06 27  
> 2875636   2013-01-16 21:12:08 282 
> 2875636   2013-01-16 21:51:02 6   
> 2875636   2013-01-16 22:18:34 173 
> 2875636   2013-01-16 23:02:58 318 
> 2875636   2013-01-16 23:45:37 207 
> 3018868   2013-01-16 16:01:45 18  
> 3018868   2013-01-16 16:16:45 39  
> 3018868   2013-01-16 16:22:55 656 
> 3018868   2013-01-16 16:25:54 1852    
> 3018868   2013-01-16 16:29:23 688 
> 3018868   2013-01-16 16:47:26 2258                       10177846
> 3018868   2013-01-16 16:57:41 572 
> 3018868   2013-01-16 17:06:47 1431    
> 3018868   2013-01-16 17:18:32 29  
> 3018868   2013-01-16 17:21:57 45  
> 3018868   2013-01-16 17:29:23 16  
> 3018868   2013-01-16 17:36:47 490
> 
> ```
> 
> 

EXPECTED RESULT

```
user_id starttime           visit_duration_seconds  order_number        RESULT
2875636 2013-01-16 18:03:50 61                                      61
2875636 2013-01-16 18:08:18 151                                     212
2875636 2013-01-16 18:15:43 33                                      245
2875636 2013-01-16 18:16:37 13                                      258
2875636 2013-01-16 18:18:01 2011                     10177888           0
2875636 2013-01-16 18:24:35 1172                     10177884           0
2875636 2013-01-16 18:32:03 4731                                        4731
2875636 2013-01-16 18:33:27 407                                     5138
2875636 2013-01-16 18:37:29 74                                      5212
2875636 2013-01-16 18:48:55 80                                      ...
2875636 2013-01-16 19:05:00 1955                                        ...
2875636 2013-01-16 19:14:12 326                                     ...
2875636 2013-01-16 19:23:39 972 
2875636 2013-01-16 19:33:05 5440    
2875636 2013-01-16 19:35:48 43  
2875636 2013-01-16 19:41:10 66  
2875636 2013-01-16 19:42:03 100 
2875636 2013-01-16 19:42:12 2414                     10177940
2875636 2013-01-16 19:49:05 432                  10177925
2875636 2013-01-16 19:50:19 183 
2875636 2013-01-16 19:52:46 2061    
2875636 2013-01-16 19:52:53 400 
2875636 2013-01-16 20:00:47 338 
2875636 2013-01-16 20:08:58 216 
2875636 2013-01-16 20:14:21 58  
2875636 2013-01-16 20:14:26 196 
2875636 2013-01-16 20:19:14 2189    
2875636 2013-01-16 20:21:29 424 
2875636 2013-01-16 20:24:42 999 
2875636 2013-01-16 21:01:39 1810    
2875636 2013-01-16 21:02:54 525 
2875636 2013-01-16 21:10:06 27  
2875636 2013-01-16 21:12:08 282 
2875636 2013-01-16 21:51:02 6   
2875636 2013-01-16 22:18:34 173 
2875636 2013-01-16 23:02:58 318 
2875636 2013-01-16 23:45:37 207 
3018868 2013-01-16 16:01:45 18  
3018868 2013-01-16 16:16:45 39  
3018868 2013-01-16 16:22:55 656 
3018868 2013-01-16 16:25:54 1852    
3018868 2013-01-16 16:29:23 688 
3018868 2013-01-16 16:47:26 2258                       10177846
3018868 2013-01-16 16:57:41 572 
3018868 2013-01-16 17:06:47 1431    
3018868 2013-01-16 17:18:32 29  
3018868 2013-01-16 17:21:57 45  
3018868 2013-01-16 17:29:23 16  
3018868 2013-01-16 17:36:47 490 

```