Oracle rownum vs Postgres

rownum test

create table rownum_tst (
id integer,
vc varchar(20)
);

insert into rownum_tst(id,vc) values(1,'4');
insert into rownum_tst(id,vc) values(2,'4,5');

select * from
(select rownum as position, vc from rownum_tst)
where vc = '4,5';

--postgres gives 1 4,5
--ora      gives 2 4,5

--change into to give same result

select * from
(select row_number() OVER (order by id)  as position, vc from rownum_tst)
where vc = '4,5';