49.组合 Products 表中的产品名称和 Custom

select prod_name
from Products
inner join
select cust_name
from Customers
order by prod_name

select prod_name
from Products
left join
select cust_name
from Customers
order by prod_name

select prod_name
from Products
union all
select cust_name
from Customers

select prod_name
from Products
union all
select cust_name
from Customers
order by prod_name