Subtract values from line above the current line in MySQL - mysql

Question

I've the following table:
| id | Name | Date of Birth | Date of Death | Result |
| 1 | John | 3546565 | 3548987 | |
| 2 | Mary | 5233654 | 5265458 | |
| 3 | Lewis| 6546876 | 6548752 | |
| 4 | Mark | 6546546 | 6767767 | |
| 5 | Steve| 6546877 | 6548798 | |
And I need to do this for the whole table:
Result = 1, if( current_row(Date of Birth) - row_above_current_row(Date of Death))>X else 0
To make things easier, I guess, I created the same table above but with 2 extra id fields: id_minus_one and id_plus_one
Like this:
| id | id_minus_one | id_plus_one |Name | Date_of_Birth | Date_of_Death | Result |
| 1 | 0 | 2 |John | 3546565 | 3548987 | |
| 2 | 1 | 3 |Mary | 5233654 | 5265458 | |
| 3 | 2 | 4 |Lewis| 6546876 | 6548752 | |
| 4 | 3 | 5 |Mark | 6546546 | 6767767 | |
| 5 | 4 | 6 |Steve| 6546877 | 6548798 | |
So my approach would be something like (in pseudo code):
for id=1, ignore result. (Because there is no row above)
for id=2, Result = 1 if( (Where id=2).Date_of_Birth - (where id_minus_one=id-1).Date_of_Death )>X else 0
for id=3, Result = 1 if( (Where id=3).Date_of_Birth - (where id_minus_one=id-1).Date_of_Death)>X else 0
and so on for the whole table...
Just ignore id_plus_one if there is no need for it, I'll use it later for the same thing. So, if I manage to do this for id_minus_one I'll manage for id_plus_one as they are the same algorithm.
My question is how to pass that pseudo code into SQL code, I can't find a way to relate both ids in just one select.
Thank you!

Answer 1

As you describe this, it is just a self join with some logic on the select:
select t.*,
((t.date_of_birth - tprev.date_of_death) > x) as flag
from t left outer join
t tprev
on t.id_minus_one = tprev.id