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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
? 1 2 3 4 5CREATE TABLE MonthlyOrders(
ordermonth DATE,
ordernum INT UNSIGNED,
PRIMARY KEY (ordermonth)
);
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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
? 1 2 3 4 5 6 7 8 9 10SELECT
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:
? 1DATE_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
? 1c.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。
? 1 2 3 4 5 6 7 8 9 10 11SELECT
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
希望本文所述对大家MySQL数据库计有所帮助。
原文链接：https://www.cnblogs.com/chenqionghe/p/4679800.html
