code | user_id | register_date | time_difference
-------+-----------+---------------+----------------
AiK4JJ | kcy2000ok | 2012-01-31 | 17:25:41
unBG1D | gktoql | 2012-01-31 | 17:25:35
vzqeWU | gktoql | 2012-01-31 | 17:25:32
vvkOSd | gktoql | 2012-01-31 | 17:25:32
uwhbGt | ppsh | 2012-01-31 | 17:25:28
unBG1D | judyssi | 2012-01-31 | 17:25:27
vvkOSd | judyssi | 2012-01-31 | 17:25:24
I wanna calculate time difference in seconds between recent date and previous date.
Can you help me to build MySql query?