SQL zero-to-many column comparison

Say I have two columns in a table, a and b. For each value of a, there can be zero-to-many values of b. If the columns are sorted by a, then by b, what is the most efficient way to mark the first value of b which is greater than the corresponding value of a in a new third column? See simplified example below.

Initial Table

a	b
10	8
10	10
10	11
10	14
20	22
20	25
30	25
30	28

Desired Modified Table

a	b	first_greater
10	8	0
10	10	0
10	11	1
10	14	0
20	22	1
20	25	0
30	25	0
30	28	0

Answer

You don’t suggest a specific RDBMS but I would think the following is not too inneficient, using a simple window function and conditional case.

select a, b,
    case when b > a
      and Row_Number() 
         over (partition by a, case when b > a then 1 end order by b)=1
     then 1 else 0 
   end as first_greater
from t