PL/SQL :: Partition By Group?

below is the create and insert script.

create table sal_group (g_id number(10),sal_rand number(20));
/
INSERT INTO sal_group values(1,5000)
/
INSERT INTO sal_group values(1,2000)
/
INSERT INTO sal_group values(1,4000)

[code]...

/I have tried

SELECT g_id,sal_rand,
case when row_number() over (order by g_id) = count(*) over () then 'yes' else null end as row_check
  FROM sal_group output:

G_ID    SAL_RAND    ROW_CHECK

1       4000   
1       2000   

[code]....