Unique row based on two columns and single column

Question

Dear Members,
I have a table which contains duplicate rows, for which a query should be able to fetch the unique row from the table. Here the unique is not based on one column, but it should be on two columns and also check for uniqueness on one column.
create table addr ( firstname varchar2(10), lastname varchar2(10), area varchar2(3));
insert into addr values('bob', 'james', '1');
insert into addr values('bob', 'james', '1');
insert into addr values('harry', 'bert', '1');
insert into addr values('jimmy', 'bert', '1');
insert into addr values('sam', 'mac', '1');
insert into addr values('sam', 'knight', '1');
insert into addr values('tom', 'sand', '1');
insert into addr values('cat', 'mud', '1');
The output of query should contain 3 rows.
bob - james
harry - bert or jimmy - bert [ either one of them, but not both ]
sam - mac or sam - knight [ either one of them, but not both ]
tom - sand
cat - mud
SELECT firstname, lastname as total from addr WHERE area = '1' GROUP by firstname,lastname; This does not take of single column duplication..
Any suggestions..

Answer 1

SQL> with t_data
as
select 'bob' as firstname, 'james' as lastname, '1' as area from dual union all
select 'bob', 'james', '1' from dual union all
select 'harry', 'bert', '1' from dual union all
select 'jimmy', 'bert', '1' from dual union all
select 'sam', 'mac', '1' from dual union all
select 'sam', 'knight', '1' from dual union all
select 'tom', 'sand', '1' from dual union all
select 'cat', 'mud', '1' from dual
SELECT
        firstname,
        lastname,
        area
FROM
                SELECT
                        t.*,
                        row_number() over(partition BY firstname order by 1) rn,
                        row_number() over(partition BY lastname order by 1) rn1
                FROM
                        t_data t
WHERE
        rn     = 1
AND rn1 =1 ; 
FIRSTNAME       LASTNAME        AREA
bob             james           1
cat             mud             1
jimmy           bert            1
sam             knight          1
tom             sand            1
SQL>