With语句可以在查询中做成一个临时表/View，用意是在接下来的SQL中重用，而不需再写一遍。
With Clause方法的优点： 增加了SQL的易读性，如果构造了多个子查询，结构会更清晰。
示例：
with soloemp as (select distinct salary from hy_emp)
select avg(salary) from
(select dense_rank() over (order by salary) as seq, dense_rank() over (order by salary desc) as revseq,salary from soloemp) a
where abs(a.seq-a.revseq)<=1--2020-04-14--
来源：oschina
链接：https://my.oschina.net/u/4407242/blog/3235773