create table test1
(
    id  int primary key,
    ida int not null,
    dk  int not null,
    s   int not null
);

INSERT INTO public.test1 (id, ida, dk, s) VALUES (1, 1, 1, 20040);
INSERT INTO public.test1 (id, ida, dk, s) VALUES (2, 1, 1, 1070);
INSERT INTO public.test1 (id, ida, dk, s) VALUES (3, 1, 2, 11040);
INSERT INTO public.test1 (id, ida, dk, s) VALUES (4, 2, 1, 12514);
INSERT INTO public.test1 (id, ida, dk, s) VALUES (5, 2, 2, 1530);

select *,
       (
               COALESCE((select sum(s) from test1 where dk = 1 and id <= t1.id), 0)
               -
               COALESCE((select sum(s) from test1 where dk = 2 and id <= t1.id), 0)
           )
from test1 as t1;