Question

您好我正在使用此sql查询获取基于月份的最近12个月的图表来表示图表：

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

然而，如果一个月没有记录，它不会按预期包含在结果集中，我正在用php做很多计算来完成我想要的。

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数，如果一个月有0个驱动器，则必须包含它 - 显示在结果中集。

Answer 1

您需要使用包含每个月行的表进行外部联接。假设您没有这样的表，可以使用硬编码的UNION查询动态创建它：

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都会在数据列中有一行NULL。

Mysql过去12个月按月记录的总和

1 个答案: