SELECT
			SUM (
				(
					TO_DAYS( LEAST( s_date_end, r_date_last ) ) -
					TO_DAYS( GREATEST( r_date_from, s_date_start ) )
				)  + 1 ) * sp_price AS total_price

FROM 		reservations
INNER JOIN 	reservation_items
		ON 	ri_reservationsid = r_id
INNER JOIN 	products
		ON 	ri_productsid = p_id
INNER JOIN 	product_groups
		ON 	if( p_type = "house", p_house_public_productgroupsid, p_productgroupsid ) = pg_id
INNER JOIN 	season_prices
		ON 	sp_productgroupsid = pg_id
INNER JOIN 	seasons
		ON 	s_id = sp_seasonsid
		AND r_date_from <= s_date_end
		AND r_date_last >= s_date_start
WHERE 		( ri_parentid = 0	OR ri_parentid IS NULL)
			AND ri_id =1
group by	r_id

function get_total_price(reservation_id) {
-- return result of above select
}
}