SELECT N.id, N.name,
	CONCAT(
        "[",
        	GROUP_CONCAT(
                CONCAT("{shop:'",CONVERT(S.name USING utf8),"',"),
        	   CONCAT("count:'",CONVERT(P.count USING utf8),"'}")
                )
        ,"]"
        ) as data
FROM `modx_products_nomenclature` N	
	LEFT JOIN `modx_shops` S ON S.active = 1
    LEFT JOIN `modx_warehouse_products` P ON P.product_id = N.id and S.warehouse_id = P.warehouse_id
GROUP BY N.id

id 1
name G1
data [{shop:'A', count:'10'}]
.....
id 3
name G1
data [{shop:'A', count:'10'}, {shop:'B', count:'10'}]