滑动订单问题是指为每个月返回上一年度（季度或月度等）的滑动订单数。
即：某个月份N，返回从（N-11）月到N月的订单总数。（架设月份序列中不存在间断）。

首先创建一个测试表

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

再插入一些数据

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

最后返回的结果集应该为：

解决方案

select
date_format(a.ordermonth, '%Y-%m') as from_month,
date_format(b.ordermonth, '%Y-%m') as to_month,
sum(c.ordernum) as orders
from monthly_orders a
join monthly_orders b
on date_add(a.ordermonth, interval 11 month) = b.ordermonth
join monthly_orders c
on c.ordermonth between a.ordermonth and b.ordermonth
group by a.ordermonth,b.ordermonth;

该查询对monthly_orders表进行自联接，a表用做下边界(from_month)，b表用做上边界(to_month)。
联接条件为：date_add(a.ordermonth, interval 11 month) = b.ordermonth。
例如2010年2月将匹配2011年1月
完成此次自联接操作之后，需要对订单进行统计，这时需要在进行一次自联接，得到范围内每个月的订单数量，因此联接条件为c.ordermonth between a.ordermonth and b.ordermonth 。

按照上述方法，我们还可以统计每个季度订单的详情，作为环比和同比增长的比较依据。

即

解决方案：

select
date_format(a.ordermonth,\'%Y-%m\') as from_month,
date_format(b.ordermonth,\'%Y-%m\') as to_month,
sum(c.ordernum) as orders
from monthly_orders a
join monthly_orders b
on date_add(a.ordermonth, interval 2 month) = b.ordermonth
and month(a.ordermonth) % 3 = 1
join monthly_orders c
on c.ordermonth between a.ordermonth and b.ordermonth
group by a.ordermonth,b.ordermonth;

ITPub博客

MySQL 滑动订单问题

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