Mysql 近12个月按月记录总和

Question

您好，我正在使用此 sql 查询获取基于图表表示月份的最近 12 个月的记录:

SELECT DATE_FORMAT(drives.timestamp, "%b") AS Month,
                         DATE_FORMAT(drives.timestamp, "%d-%m-%Y %H:%i:%s") AS Exact_date,
                         drives.departure,
                         drives.destination,
                         drives.route,
                         CONCAT(drivers.name, " ", drivers.surname) as driver,
                         drivers.id as driver_id
                         FROM drives, drivers WHERE drives.driver = drivers.id 
                         AND drives.timestamp > DATE_SUB(now(), INTERVAL 12 MONTH) ORDER BY drives.timestamp Asc

但是，如果一个月没有记录，则它不会按预期包含在结果集中，我正在使用 php 进行大量计算以完成我想要的。

我的问题是:有没有办法检索一个简单的结果集，其中包含过去 12 个月每个月的驱动器总和，如果一个月有 0 个驱动器，则它也必须包含在结果中显示设置。

Answer 1

您需要对包含每个月的行的表进行外连接。假设您没有这样的表，您可以使用硬编码的 UNION 查询即时创建它:

SELECT * FROM
    (SELECT DATE_FORMAT(now(), "%b") as Month
     UNION
     SELECT DATE_FORMAT(now() - INTERVAL 1 MONTH), "%b")
     UNION
     SELECT DATE_FORMAT(now() - INTERVAL 2 MONTH), "%b")
     UNION
     ...
     SELECT DATE_FORMAT(now() - INTERVAL 11 MONTH), "%b")) AS Months
LEFT JOIN (SELECT DATE_FORMAT(drives.timestamp, "%b") AS Month,
                 drives.timestamp,
                 DATE_FORMAT(drives.timestamp, "%d-%m-%Y %H:%i:%s") AS Exact_date,
                 drives.departure,
                 drives.destination,
                 drives.route,
                 CONCAT(drivers.name, " ", drivers.surname) as driver,
                 drivers.id as driver_id
                 FROM drives, drivers WHERE drives.driver = drivers.id 
                 AND drives.timestamp > DATE_SUB(now(), INTERVAL 12 MONTH)) data
ON Months.Month = data.Month
ORDER BY data.timestamp

任何没有记录的月份的数据列中都会有一行 NULL。