How to find difference between two rows with conditions

Question

name      point
----------
steve     207
Mary      203
steve     205
steve     200
steve     139
Mary      300

I want to get the difference between the rows with condition eqn = [ (row + 1) - row] where name = steve, so I would ideally want it to be,

steve 2   //207 - 0
steve 5   //205 - 207
steve 61  //200 - 205
steve 139 //139 - 200

there are codes available to find the difference between consecutive rows. but it will not work when condition is added.

Answer 1

Edited due OP comment I have changed query to match exactly your request.

LAG can helps you:

  select name, 
    coalesce( 
        point - lag( point , 1, Null ) over (order by point),
        point)
    as diff,
    point || '-' ||
    LEAD( point , 1, 0 ) over (order by point) as prev_point
  from t   
  where name = 'steve'  
  order by point desc

Results:

|  NAME | DIFF | PREV_POINT |
-----------------------------
| steve |    2 |      207-0 |
| steve |    5 |    205-207 |
| steve |   61 |    200-205 |
| steve |  139 |    139-200 |