此处以scott用户下emp表和dept表为例:
with sql1 as (select emp.deptno from emp), sql2 as (select dept.deptno from dept) select deptno from sql1 union all select deptno from sql2;
http://blog.163.com/fly_sky_java/blog/static/14042223420125194455688/
with sql1 as (select emp.deptno from emp), sql2 as (select dept.deptno from dept) select deptno from sql1 union all select deptno from sql2;