Question

I would prefer to get this done in MySQL.

Table:

tracker | user_id | timestamp | action
1         1         1234        1
2         2         1236        9
3         1         1237        2

I need to find all users who had the action of 1, and subtract the timestamp from their next action. Meaning, User 1’s 1234 timestamp will be subtracted from his 1237 timestamp.

The idea is to calculate how long the user spent at action 1 until they went somewhere else.

Getting the first timestamp is easy. One idea is to record the tracker value, and then do a subquery for where user_id pops up again with a tracker higher than the first. In the example: WHERE user_id = 1 AND tracker > 1

Is there a more optimal solution?

Answer 1

Probably this helps you. This will join to all future actions

SELECT t1.*, 
       t2.`timestamp` - t1.`timestamp`
FROM   table t1 
       JOIN table t2 
         ON t1.user_id = t2.user_id 
            AND t2.tracker > t1.tracker 
WHERE  t1.`action` = 1;

you probably want to extend to add also a condition to get the next one only.

this is some ad-hoc query, and can’t precisely tell if will work or not
This is suppose to select only the next one for that user.

SELECT t1.*, 
       t2.`timestamp` - t1.`timestamp` 
FROM   table t1 
       JOIN table t2 
         ON t1.user_id = t2.user_id 
            AND t2.tracker = (SELECT Min(tracker) 
                              FROM   table t3 
                              WHERE  t3.user_id = t1.user_id 
                                     AND t3.tracker > t1.tracker) 
WHERE  t1.`action` = 1;