how to get diff between subsequent rows without lag

Question

I have

id value
1 12
1 15
1 17
1 22
1 22
1 23

And I need like this

id  value
1 --
1 3
1 2
1 5
1 0
1 1

Could you tell me, how to achive this?

Answer 1

You can try the below -

select id, 
      value-max(value) over(order by id rows between 1 preceding and 1 preceding) as value
from tablename