distinct values from multiple fields within one table ORACLE SQL

Question

How can I get distinct values from multiple fields within one table with just one request.

Option 1

SELECT WM_CONCAT(DISTINCT(FIELD1)) FIELD1S,WM_CONCAT(DISTINCT(FIELD2)) FIELD2S,..FIELD10S
  FROM TABLE;

WM_CONCAT is LIMITED

Option 2

select DISTINCT(FIELD1) FIELDVALUE, 'FIELD1' FIELDNAME
       FROM TABLE
UNION
select DISTINCT(FIELD2) FIELDVALUE, 'FIELD2' FIELDNAME
       FROM TABLE
... FIELD 10

is just too slow

Answer 1

if you were scanning a small range in the data (not full scanning the whole table) you could use WITH to optimise your query e.g:

WITH a AS 
(SELECT field1,field2,field3..... FROM TABLE WHERE condition)
SELECT field1 FROM a
UNION   
SELECT field2 FROM a
UNION   
SELECT field3 FROM a
.....etc

Answer 2

For my problem, I had

WL1   ...   WL2   ...  correlation
A            B             0.8
B            A             0.8
A            C             0.9
C            A             0.9

how to eliminate the symmetry from this table?

    select WL1, WL2,correlation from
    table
    where least(WL1,WL2)||greatest(WL1,WL2) = WL1||WL2
    order by WL1

this gives

WL1   ...   WL2   ...  correlation
A            B             0.8
A            C             0.9

:)