SELECT
house, AVG(salary) AS median

FROM (
	SELECT
	h.id as house,
	x.salary

	FROM
	person x,
	person y,
	house h

	WHERE
	x.houseid=h.id AND
	y.houseid=h.id

	GROUP BY
	x.salary, h.id

	HAVING
	(
		(
			SUM(SIGN(1-SIGN(y.salary-x.salary))))>=floor((COUNT(*)+1)/2
		)
	)
	AND
	(
		(
			SUM(SIGN(1+SIGN(y.salary-x.salary))))>=floor((COUNT(*)+1)/2
		)
	)
	ORDER BY h.id
) AS tmp

GROUP BY
house
;