SQL difference between two rows with timestamp

Question

Im working on with SQL on PostgreSQL I have this table that describes images of cars with columns camera , whn and reg

Camera is int,whn is timestamp string(eg 2007-02-25 07:51:10) and reg is string

I am doing this assignment and im stuck on:

"Print the register plate(reg) of cars which have been photographed twice by the same camera or different and the difference between the photos is a minute or less"

Does anybody know how i can express this difference between two different rows of the column whn that needs to be equal or less than 60 seconds?

Answer 1

1. Sort your table by timestamp.
2. Use lag() from windows function to get row below current row.
3. Use extract() to see different between two timestamp.