create table t1 (f1 number(10),f2 number(10),f3 number(10),f4 number(10));

insert into t1 values (1,10,20,30);
insert into t1 values (1,5,2,4);
insert into t1 values (1,2,4,3);
insert into t1 values (2,10,20,30);
insert into t1 values (2,5,1,8);
insert into t1 values (3,5,55,5);
insert into t1 values (4,6,6,6);
insert into t1 values (4,33,36,33);
insert into t1 values (5,6,6,6);
insert into t1 values (5,88,88,88);

select f1,f2,f3,f4 from 
(select f1,f2,f3,f4,row_number() over(partition by f1 order by f1) rn
from t1)
where rn=1

    f1   f2   f3   f4  
---------------------------------------
1    1    10    20    30
2    2    10    20    30
3    3    5    55    5
4    4    6    6    6
5    5    6    6    6