How to group by below query?

Question

Hi All,
I have below query,
SELECT username,firstname,lastname,country
FROM emp e1
WHERE EXISTS (
SELECT 1
FROM emp
WHERE e1.lastname = firstname
AND e1.firstname) = lastname )
OR EXISTS (
SELECT 1
FROM emp
WHERE lastname = e1.lastname
AND firstname) = e1.firstname )
and the result of the query is
USERNAME,      FIRSTNAME,     LASTNAME, COUNTRY
1,     b6,     a6, CH
2,     a6,     b6,     CH
3,     a1,     b1,     CH
4,     b1,     a1,     CH
5,     a2,     b2,     CH
6,     a2,     b2,     CH
7,     b1,      a1,     CH
8,     b1,     a1,     CH
9,     b2,     a2,     CH
10,     b2, a2,     CH
now i have to group all the firstname and lastname which are haviing values
1) a1,b1 and b1,a1
2) a2,b2 and b2,a2
3) a6,b6 and b6,a6
Can you please help me in this?
Thanks in advance.
Edited by: user9258447 on Jul 27, 2010 6:16 AM

Answer 1

Welcome to the forum!
select least (first_name, last_name)
     , greatest (first_name, last_name)
     , ctry     
  from test
group by least (first_name, last_name)
        , greatest (first_name, last_name)
        , ctryas in
SQL> with test as
  2  (
  3  select 1 username,    'b6' first_name,    'a6' last_name, 'CH' ctry from dual union all
  4  select 2 username,    'a6' first_name,    'b6' last_name,    'CH' ctry from dual union all
  5  select 3 username,    'a1' first_name,    'b1' last_name,    'CH' ctry from dual union all
  6  select 4 username,    'b1' first_name,    'a1' last_name,    'CH' ctry from dual union all
  7  select 5 username,    'a2' first_name,    'b2' last_name,    'CH' ctry from dual union all
  8  select 6 username,    'a2' first_name,    'b2' last_name,    'CH' ctry from dual union all
  9  select 7 username,    'b1' first_name, 'a1' last_name,    'CH' ctry from dual union all
10  select 8 username,    'b1' first_name,    'a1' last_name,    'CH' ctry from dual union all
11  select 9 username,    'b2' first_name,    'a2' last_name,    'CH' ctry from dual union all
12  select 1 username0,  'b2' first_name, 'a2' last_name,  'CH' ctry from dual
13  )
14  select least (first_name, last_name)
15       , greatest (first_name, last_name)
16       , ctry     
17    from test
18   group by least (first_name, last_name)
19          , greatest (first_name, last_name)
20          , ctry
21  /
LE GR CT
a1 b1 CH
a2 b2 CH
a6 b6 CH