唯一性约束(Unique constraints):Oracle9i允许对视图的任意一栏定义唯一性约束。
主键(Primary key):我们可以直接给视图定义主键约束。
外键(Foreign Key):只要视图有依赖于其它基表的外键,那么就会直接存在外键参考完整性。
alter view
widget_orders
add constraint
widget_orders_pk
primary key
(cust_name, order_date, product_name)
disable novalidate;
create or replace view
widget_orders
as
select
cust_name,
order_date,
product_name,
sum(qty*price) total cost
from
customer
natural join
orders
natural join
order_item
natural join
product
where
product_type = 'widget';