SET @rn := 0;
SET @gn := 0;

SELECT group_num, pa_id
FROM (
SELECT t2.group_num, MIN(t2.price_torg) as min, MAX(t2.price_torg) as max
FROM (
SELECT *
		,IF (@rn % 12 = 0, @gn:=@gn+1, @gn) AS 'group_num'
		,@rn:=@rn+1
FROM (
	SELECT
		pd.*
		,pa.avalaible_gen
		,pa.price_torg
	FROM migrate.PA_DR pd
	LEFT JOIN prices_all pa ON pd.pd_pa_id = pa.id
	LEFT JOIN seo_available_razdel sr ON pd.pd_dr_id = sr.dok_razdel_id
	WHERE 1
		AND pa.price_torg >= sr.min_available_price
		AND pd.pd_dr_id = 242
		AND pa.avalaible_gen = 1
	ORDER BY pa.price_torg ASC
) t
) t2

GROUP BY t2.group_num
) t3
LEFT JOIN (
	SELECT
		pd.*
		,pa.avalaible_gen
		,pa.price_torg
,pa.id as pa_id
	FROM migrate.PA_DR pd
	LEFT JOIN prices_all pa ON pd.pd_pa_id = pa.id
	LEFT JOIN seo_available_razdel sr ON pd.pd_dr_id = sr.dok_razdel_id
	WHERE 1
		AND pa.price_torg >= sr.min_available_price
		AND pd.pd_dr_id = 242
		AND pa.avalaible_gen = 0
) t4 ON t4.price_torg >= t3.min AND t4.price_torg  <= t3.max

ORDER BY group_num