Oracle-SQL-按月统计自助终端交易量

SQL实现的目标：

规则，  每天每种交易最多统计3笔

完成按月统计任务

用到的知识点总结：

1） case when的使用；

case  when count(transQK.tran_amt) > 3 then 3  else count(transQK.tran_amt) end  count
case  when dayQK.count is null then 0 else dayQK.count end

2）left join的使用；   left join 中可以写where 的条件

--外连接取款
left join
    (
    select
        case  when sum(dayQKIn.count) is null then 0 else sum(dayQKIn.count)  end count,
        case  when sum(dayQKIn.money) is null then 0 else sum(dayQKIn.money)  end money,
        term_id_in
    from
    (
        select
            case  when count(transQK.tran_amt) > 3 then 3  else count(transQK.tran_amt) end  count,
            case  when sum(transQK.tran_amt) is null then 0 else sum(transQK.tran_amt)  end  money,
            to_char(to_date(transQK.p_req_date, ‘yyyyMMdd‘), ‘dd‘) p_req_date,
            term_id_in
        from
            BIZ_OPER_TRANS transQK
        where
        -- 取款 便民取款
            (transQK.P_TRANS_CODE=‘1011101‘ or transQK.P_TRANS_CODE=‘1011231‘)
            and     transQK.p_req_date between to_char(add_months(last_day(sysdate)+1,-2),‘yyyyMMdd‘) and to_char(add_months(last_day(sysdate),-1),‘yyyyMMdd‘)
        group by
            term_id_in,P_TRANS_CODE,to_char(to_date(transQK.p_req_date, ‘yyyyMMdd‘), ‘dd‘)
        ) dayQKIn
         group by dayQKIn.term_id_in
    ) dayQK
    on dayQK.term_id_in=term.TERMINAL_ID 

3） 时间函数 表示  上个月第一天  、 上个月最后一天

transCX.p_req_date between to_char(add_months(last_day(sysdate)+1,-2),‘yyyyMMdd‘) and to_char(add_months(last_day(sysdate),-1),‘yyyyMMdd‘)

4）四舍五入   月笔数/天数

round(( case  when dayQK.count is null then 0 else dayQK.count end +
    case  when dayCK.count is null then 0 else dayCK.count end +
    case  when dayZZ.count is null then 0 else dayZZ.count end +
    case  when dayDJ.count is null then 0 else dayDJ.count end +
    case  when dayCX.count is null then 0 else dayCX.count end )
    /(1+to_char(add_months(last_day(sysdate),-1),‘yyyyMMdd‘)-to_char(add_months(last_day(sysdate)+1,-2),‘yyyyMMdd‘)),2)

5)  最终的SQL