这是表的基本设置(仅存在相关列的DDL)。 MySQL版本8.0.15
目的是显示订单之间的日期差异间隔的平均值。
CREATE TABLE final (
prim_id INT(11) NOT NULL AUTO_INCREMENT,
order_ID INT(11) NOT NULL,
cust_ID VARCHAR(45) NOT NULL,
created_at DATETIME NOT NULL,
item_name VARCHAR(255) NOT NULL,
cust_name VARCHAR(255) NOT NULL,
PRIMARY KEY (prim_id),
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
AUTO_INCREMENT=145699
附加信息:
cust ID -> cust_name (one-to-many)
cust_ID -> order_ID (one-to-many)
order ID -> item_name (one-to-many)
order ID -> created_at (one-to-one)
prim_id -> *everything* (one-to-many)
我曾想过使用min(created_at)和max(created_at),但这将排除最旧和最新之间的所有订单。我需要一个更精致的解决方案。
最终结果应该是这样的:
有关所有订单之间的平均时间间隔的信息(不仅是最小值和最大值,因为经常有两次以上)以天为单位,在显示客户名称(cust_name)的列旁边。
如果我说得对,你可以使用子查询来获取前一个订单的日期。使用datediff()
来获取日期和avg()
之间的差异,以获得这些差异的平均值。
SELECT f1.cust_id,
avg(datediff(f1.created_at,
(SELECT f2.created_at
FROM final f2
WHERE f2.cust_id = f1.cust_id
AND (f2.created_at < f1.created_at
OR f2.created_at = f1.created_at
AND f2.order_id < f1.order_id)
ORDER BY f2.created_at DESC,
f2.order_id DESC
LIMIT 1)))
FROM final f1
GROUP BY f1.cust_id;
编辑:
如果一个订单ID可以有更多行,正如KIKO软件提到的那样,我们需要从不同的订单集中执行SELECT
,例如:
SELECT f1.cust_id,
avg(datediff(f1.created_at,
(SELECT f2.created_at
FROM (SELECT DISTINCT f3.cust_id,
f3.created_at,
f3.order_id
FROM final f3) f2
WHERE f2.cust_id = f1.cust_id
AND (f2.created_at < f1.created_at
OR f2.created_at = f1.created_at
AND f2.order_id < f1.order_id)
ORDER BY f2.created_at DESC,
f2.order_id DESC
LIMIT 1)))
FROM (SELECT DISTINCT f3.cust_id,
f3.created_at,
f3.order_id
FROM final f3) f1
GROUP BY f1.cust_id;
如果具有不同客户ID或不同创建时间戳的订单可以有两行,则可能会失败。但在这种情况下,数据只是完全垃圾,需要先纠正。
第二编辑:
或者,如果这些可能不同,则获取每个订单的最大创建时间戳:
SELECT f1.cust_id,
avg(datediff(f1.created_at,
(SELECT f2.created_at
FROM (SELECT max(f3.cust_id) cust_id,
max(f3.created_at) created_at,
f3.order_id
FROM final f3
GROUP BY f3.order_id) f2
WHERE f2.cust_id = f1.cust_id
AND (f2.created_at < f1.created_at
OR f2.created_at = f1.created_at
AND f2.order_id < f1.order_id)
ORDER BY f2.created_at DESC,
f2.order_id DESC
LIMIT 1)))
FROM (SELECT max(f3.cust_id) cust_id,
max(f3.created_at) created_at,
f3.order_id
FROM final f3
GROUP BY f3.order_id) f1
GROUP BY f1.cust_id;