--1000以内的均是公司走向全国之前的本城市的老客户:) 
update customers 
set city_name='北京' 
where customer_id<1000

--这次提取的数据都是VIP，且包括新增的,所以顺便更新客户类别 
update customers a -- 使用别名 
set customer_type='01' --01 为vip，00为普通 
where exists (select 1 
from tmp_cust_city b 
where b.customer_id=a.customer_id 
)

update customers a -- 使用别名 
set city_name=(select b.city_name from tmp_cust_city b where b.customer_id=a.customer_id) 
where exists (select 1 
from tmp_cust_city b 
where b.customer_id=a.customer_id 
) 
-- update 超过2个值 
update customers a -- 使用别名 
set (city_name,customer_type)=(select b.city_name,b.customer_type 
from tmp_cust_city b 
where b.customer_id=a.customer_id) 
where exists (select 1 
from tmp_cust_city b 
where b.customer_id=a.customer_id 
)