面试遇到的订单表sql的解决方案

对于以下需求：用户表：users (user_id  int)
订单表：order_tb(user_id int, or_time  date, or_money double)
求以下用户：
一月下过单，二月份没有下过单的三月份下单用户
的如下指标：
三月份订单金额大于100的订单数，三月份第一笔订单和最后一笔订单的订单金额。（每个用户的哦）

网上求得如下解答，比自己之前写的几百行好多了。不知道有没有其它解决方案

with us1 as  (select user_id,or_time,or_money,
                    sum(nvl(case when  to_char(or_time,'MM') = '01' then 1 end,0)) over (partition by user_id) m1,
                    sum(nvl(case when  to_char(or_time,'MM') = '02' then 1 end,0)) over (partition by user_id) m2,
                    sum(nvl(case when  to_char(or_time,'MM') = '03' then 1 end,0)) over (partition by user_id) m3,
                    sum(case when  to_char(or_time,'MM') = 03 and or_money > 100 then 1 end) over (partition by user_id) cnt
                    from order_tb
                    where or_time between to_date('20170101','YYYYMMDD') and to_date('20170331','YYYYMMDD')),
mo1 as (select distinct user_id,
            case when  to_char(or_time,'MM') = 03 then first_value(or_money) over (partition by user_id order by or_time) end f1v,
            case when  to_char(or_time,'MM') = 03 then last_value(or_money) over (partition by user_id order by or_time range between unbounded preceding and unbounded following) end f3l,
            cnt from (select * from us1 where m2=0 and m1 >0 and m3 >0 and or_time between to_date('20170301','YYYYMMDD') and to_date('20170331','YYYYMMDD')))