Unnamed

id | param_id | value
1       1         foo
1       2         bar
2       1         baz
2       2         qux

--> 1, 'foo-bar'
--> 2, 'baz-qux'

Try this:
SELECT
	tn1.value || '-' || tn2.value
FROM
	table_name tn1, table_name tn2
WHERE
	tn1.id = tn2.id AND tn1.param_id != tn2.param_id