SQL - How to offset a table by 1 row

Question

How would I join a table onto itself and offset the second table to shift up by 1 row?

I want to do this in order to calculate the amount of days until the next sale date.

Answer 1

If you have data recording sales, then you would get the next date using lead():

select s.*,
       lead(saledate) over (partition by customerid order by saledate) as next_saledate
from sales s;