codes_range.sql

SELECT (SELECT
	string_agg(
		CASE
			WHEN lag IS NULL THEN to_char(code, 'FM000')
			WHEN lag <> code - 1 THEN to_char(code, '","FM000')
			WHEN lead IS NULL OR lead <> code + 1 THEN to_char(code, '"-"FM000')
		END
	, '')
FROM (SELECT code, lead(code) OVER(ORDER BY code), lag(code) OVER(ORDER BY code) FROM unnest((string_to_array(replace(code, ' ', ''), ','))::INT[]) AS code ORDER BY code) t1 WHERE lead IS NULL OR lag IS NULL OR lead <> code + 1 OR lag <> code - 1)
FROM (
		VALUES
		('001, 002'),
		('340'),
		('001, 002, 003'),
		('444, 445'),
		('406, 407'),
		('415, 416, 417'),
		('415, 416, 417, 420, 421'),
		('412, 413, 414')
) t(code);