MySQL最近12个月中按月记录的总数

Question

Hello I'm using this sql query to get the last 12 month records based on month for chart representation:

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

however if there are no records for a month it is not included in the result set as expected, and I'm doing a lot of calculations with php to accomplish what I want.

My question is this: Is there a way to retrieve a simple result set with the sum of drives of each month for the last 12 months AND if there are 0 drives for a month it must be also included-shown in the result set.

Answer 1

You need to do an outer join with a table that contains a row for each month. Assuming you don't have such a table, you can create it on the fly with a hard-coded UNION query:

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

Any months with no records will have one row with NULL in the data columns.