select datediff(day,A.rq,B.rq)
from
(select rq from order_sell_data where hth='05F0122' )A,
(select rq from data_product_indepot where hth='05F0122') B
from
(select rq from order_sell_data where hth='05F0122' )A,
(select rq from data_product_indepot where hth='05F0122') B
还有很多方法,两表连接,用临时表等.....