mysql滑动订单问题原理与解决方法实例分析

本文实例讲述了mysql滑动订单问题原理与解决方法。分享给大家供大家参考，具体如下：

先根据以下代码来创建表monthlyorders并导入一定的数据

create table monthlyorders(
ordermonth date,
ordernum int unsigned,
primary key (ordermonth)
);

insert into monthlyorders select '2010-02-01',23;
insert into monthlyorders select '2010-03-01',26;
insert into monthlyorders select '2010-04-01',24;
insert into monthlyorders select '2010-05-01',27;
insert into monthlyorders select '2010-06-01',26;
insert into monthlyorders select '2010-07-01',32;
insert into monthlyorders select '2010-08-01',34;
insert into monthlyorders select '2010-09-01',30;
insert into monthlyorders select '2010-10-01',31;
insert into monthlyorders select '2010-11-01',32;
insert into monthlyorders select '2010-12-01',33;
insert into monthlyorders select '2011-01-01',31;
insert into monthlyorders select '2011-02-01',34;
insert into monthlyorders select '2011-03-01',34;
insert into monthlyorders select '2011-04-01',38;
insert into monthlyorders select '2011-05-01',39;
insert into monthlyorders select '2011-06-01',35;
insert into monthlyorders select '2011-07-01',49;
insert into monthlyorders select '2011-08-01',56;
insert into monthlyorders select '2011-09-01',55;
insert into monthlyorders select '2011-10-01',74;
insert into monthlyorders select '2011-11-01',75;
insert into monthlyorders select '2011-12-01',14;

滑动订单问题是指为每个月返回上一年度（季度或月度）的滑动订单数，即每个月份n，返回n-11到月份n的订单总数。这里，假设月份序列中不存在间断。

执行下面的sql查询实现每个月返回上一年度的滑动订单总数

select
  date_format(a.ordermonth, '%y%m') as frommonth,
  date_format(b.ordermonth, '%y%m') as tomonth,
  sum(c.ordernum) as orders
from monthlyorders a
inner join monthlyorders b
  on date_add(a.ordermonth, interval 11 month) = b.ordermonth
inner join monthlyorders c
  on c.ordermonth between a.ordermonth and b.ordermonth
group by a.ordermonth,b.ordermonth;

运行结果如下图

该查询首先对monthlyorders表进行自连接。a表用做下边界(frommonth)，b表用做上边界(tomonth)。连接的条件为:

date_add(a.ordermonth, interval 11 month) = b.ordermonth

例如，a表中的2010年2月将匹配2011年1月。

完成自连接之后，需要对订单进行统计。这时需要再进行一次自连接，得到范围内每个月的订单数量。因此连接的条件为

c.ordermonth between a.ordermonth and b.ordermonth

基于上述方法，我们还可以统计每个季度订单的情况，以此作为和同比增长的比较依据。

select
  date_format(a.ordermonth, '%y%m') as frommonth,
  date_format(b.ordermonth, '%y%m') as tomonth,
  sum(c.ordernum) as orders
from monthlyorders a
inner join monthlyorders b
  on date_add(a.ordermonth, interval 2 month) = b.ordermonth
  and month(a.ordermonth) % 3 = 1
inner join monthlyorders c
  on c.ordermonth between a.ordermonth and b.ordermonth
group by a.ordermonth,b.ordermonth;

运行结果如下图