declare cursor previous and current element by sql server

I have a SQL Server database. Here, I keep data as int type points. Then I will do another operation with these ids, but how can I perform a mathematical operation between the declare cursor and the previous and next element in a certain table?

The rough draft algorithm is as follows;

• 16 (1.rows point data)
• 20 (2.rows point data => ABS(20-16) => 4 )
• 18 (3.rows point data => ABS(18-20) => 2 )
• 30 (4.rows point data => ABS(30-18) => 12 )
• 55 (5.rows point data => ABS(55-30) => 15 )
• 29 (6.rows point data => ABS(29-55) => 21 )
• 32 (7.rows point data => ABS(32-29) => 3 )

I will set this as stored procedure in programmability.

Currently only show point data in t-sql code;

DECLARE @point as int
DECLARE example CURSOR FOR SELECT POINT FROM data with (nolock) ORDER BY DATE ASC
    OPEN example
    FETCH NEXT FROM example INTO @point
    WHILE (@@FETCH_STATUS = 0)
    BEGIN
    select @point
    FETCH NEXT FROM example INTO @point
    END
    CLOSE example
    DEALLOCATE example

Thank you for everything..

>Solution :

You can use LAG() to peek at the previous row, according to an ordering criteria, as in lag(point) over(order by date).

For example:

select t.*,
  point - coalesce(lag(point) over(order by date), 0) as diff
from t