两表(多表)关联
update
— 被修改值由另一个表运算而来
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
)