SQLite select and group matches across columns - sql

Question

I have an SQLite table called match that has two columns: column1 and column2 that contain integer values:
column1 column2
------------------
5 6
6 8
8 9
90 91
1 20
10 20
I want to match duplicate numbers found in either columns and join them, including the matches second value, so that my search result returns would be:
5, 6, 8, 9
1, 20, 10
(notice that 90 and 91 have no matches and therefore are not included).
My 'guess' at making this is:
SELECT column1, column2
FROM match
WHERE column2
IN (SELECT column1
FROM match
GROUP BY column1 HAVING (COUNT(column1) > 0))
UNION
SELECT column1, column2
FROM match
WHERE column1
IN (SELECT column2
FROM match
GROUP BY column1 HAVING (COUNT(column2) > 0))
UNION
SELECT column1, column2
FROM match
WHERE column1
IN (SELECT column1
FROM match
GROUP BY column1 HAVING (COUNT(column1) > 1))
UNION
SELECT column1, column2
FROM match
WHERE column2
IN (SELECT column2
FROM match
GROUP BY column2 HAVING (COUNT(column2) > 1))
and the result is almost what I need:
5 6
6 8
8 9
1 20
10 20
But what I really need is to have the result grouped somehow. For example:
(5, 6, 8, 9) (1, 10, 20)
Is this possible? And is my SQL attempt over-complicated?

Answer 1

I think this is what you want: http://sqlfiddle.com/#!7/05747/9
SELECT column1 as newColumn
FROM match WHERE column1 in (
SELECT myColumn
FROM(
SELECT count(*) as cnt, myColumn
FROM (
SELECT column1 as myColumn
FROM match
UNION ALL
SELECT column2 as myColumn
FROM match
) x
GROUP BY myColumn
HAVING cnt > 1
) y
) OR column2 in (
SELECT myColumn
FROM(
SELECT count(*) as cnt, myColumn
FROM (
SELECT column1 as myColumn
FROM match
UNION ALL
SELECT column2 as myColumn
FROM match
) x
GROUP BY myColumn
HAVING cnt > 1
) y
)
UNION
SELECT column2 as newColumn
FROM match WHERE column1 in (
SELECT myColumn
FROM(
SELECT count(*) as cnt, myColumn
FROM (
SELECT column1 as myColumn
FROM match
UNION ALL
SELECT column2 as myColumn
FROM match
) x
GROUP BY myColumn
HAVING cnt > 1
) y
) OR column2 in (
SELECT myColumn
FROM(
SELECT count(*) as cnt, myColumn
FROM (
SELECT column1 as myColumn
FROM match
UNION ALL
SELECT column2 as myColumn
FROM match
) x
GROUP BY myColumn
HAVING cnt > 1
) y
)