组合查询很容易理解就是讲多个查询的结果放在一起显示 使用UNION关键字进行查询的组合
select cust_name, cust_contact, cust_email
from customers
where cust_state in('IL','IN','MI')
UNION
select cust_name,cust_contact,cust_email
from customers
where cust_name = 'Fun4All';
将两个查询的结果组合在一起通过union关键字