例如：sdy_tguide_order 、sdy_tguideg 是一个数据源，brt_tour 是另一个数据源

SELECT
	count(*)
FROM
	sdy_tguide_order o
LEFT JOIN sdy_tguide_region r ON r.r_num = o.r_region
LEFT JOIN brt_tour t ON t.id=o.t_id
LEFT JOIN sdy_tguideg tg ON tg.tg_num=o.tg_id
$condition