数据探查逻辑

select count(distinct seller_bu_id) as ct1, 
			 count(distinct seller_bu_id, management_city_id) as ct2
from mart_caterb2b.dim_seller_management_city_info

1. 如果 ct1 = ct2，说明seller_bu_id:management_city_id是n:1的关系，n是1还是多，需要继续探查
2. 如果 ct1 < ct2, 说明seller_bu_id:management_city_id是1:n的关系，n是多
3. 如果 ct1 > ct2, 说明management_city_id中有null值，比例关系需要去掉这些null值重新计算。