--创建表
create table emp01
as
select * from employees
where department_id in (70,80)
 
--
--创建表
create table emp02
as
select * from employees
where department_id in (80,90)

--查询 --并集
select * from employees
where department_id in (70,80)
union all
select * from employees
where department_id in (80,90)