How to calculate time difference between current and previous row in MySQL

Question

I have mysql table t1 like this :

What i want to do is do calculations between all rows and save the value in new coloumn called diff

TICKETID         


        

Answer 1

To get the time difference in minutes between the current and previous row, you can use timestampdiff on datenow and the previous time, which you can get via subquery:

select ticketid, datenew,
    timestampdiff(minute,datenew,(select datenew from mytable t2
        where t2.ticketid < t1.ticketid order by t2.ticketid desc limit 1)) as diff
from mytable t1

Update

Here's another way using a variable to store the previous datenew value that might be faster:

select ticketid, datenew, timestampdiff(minute,datenew,prevdatenew)
from (
    select ticketid, datenew, @prevDateNew as prevdatenew, 
      @prevDateNew := datenew
    from mytable order by ticketid
) t1