MySQL选择每月记录，即使数据不存在

本文介绍了MySQL选择每月记录，即使数据不存在的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我写了一个查询来获取用户表中的按月记录，如下所示

SELECT COUNT( `userID` ) AS total, DATE_FORMAT( `userRegistredDate` , '%b' ) AS MONTH , YEAR( `userRegistredDate` ) AS year FROM `users` GROUP BY DATE_FORMAT( FROM_UNIXTIME( `userRegistredDate` , '%b' ) )

输出:

total MONTH year --------------------------- 3 May 2013 2 Jul 2013 --------------------------

预期输出:

total MONTH year --------------------------- 0 Jan 2013 0 Feb 2013 0 Mar 2013 0 Apr 2013 3 May 2013 0 Jun 2013 2 Jul 2013 --------------------------

即使数据不存在，我也需要显示记录.该怎么做?

解决方案

关于效率，我不会说太多，因为我没有针对其他方法进行过测试，但是如果没有临时表，这似乎是一个不错的方法.

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SELECT COUNT(u.userID) AS total, m.month FROM ( SELECT 'Jan' AS MONTH UNION SELECT 'Feb' AS MONTH UNION SELECT 'Mar' AS MONTH UNION SELECT 'Apr' AS MONTH UNION SELECT 'May' AS MONTH UNION SELECT 'Jun' AS MONTH UNION SELECT 'Jul' AS MONTH UNION SELECT 'Aug' AS MONTH UNION SELECT 'Sep' AS MONTH UNION SELECT 'Oct' AS MONTH UNION SELECT 'Nov' AS MONTH UNION SELECT 'Dec' AS MONTH ) AS m LEFT JOIN users u ON MONTH(STR_TO_DATE(CONCAT(m.month, ' 2013'),'%M %Y')) = MONTH(u.userRegistredDate) AND YEAR(u.userRegistredDate) = '2013' GROUP BY m.month ORDER BY 1+1;

如果您基于日期格式进行合并，甚至可以减少工作量和查询负担.

SELECT COUNT(u.userID) AS total, DATE_FORMAT(merge_date,'%b') AS month, YEAR(m.merge_date) AS year FROM ( SELECT '2013-01-01' AS merge_date UNION SELECT '2013-02-01' AS merge_date UNION SELECT '2013-03-01' AS merge_date UNION SELECT '2013-04-01' AS merge_date UNION SELECT '2013-05-01' AS merge_date UNION SELECT '2013-06-01' AS merge_date UNION SELECT '2013-07-01' AS merge_date UNION SELECT '2013-08-01' AS merge_date UNION SELECT '2013-09-01' AS merge_date UNION SELECT '2013-10-01' AS merge_date UNION SELECT '2013-11-01' AS merge_date UNION SELECT '2013-12-01' AS merge_date ) AS m LEFT JOIN users u ON MONTH(m.merge_date) = MONTH(u.userRegistredDate) AND YEAR(m.merge_date) = YEAR(u.userRegistredDate) GROUP BY m.merge_date ORDER BY 1+1;

两个查询的实时演示.

I wrote a query to get month-wise record in user table as follows

SELECT COUNT( `userID` ) AS total, DATE_FORMAT( `userRegistredDate` , '%b' ) AS MONTH , YEAR( `userRegistredDate` ) AS year FROM `users` GROUP BY DATE_FORMAT( FROM_UNIXTIME( `userRegistredDate` , '%b' ) )

Output:

total MONTH year --------------------------- 3 May 2013 2 Jul 2013 --------------------------

Expected Output:

total MONTH year --------------------------- 0 Jan 2013 0 Feb 2013 0 Mar 2013 0 Apr 2013 3 May 2013 0 Jun 2013 2 Jul 2013 --------------------------

I need to show the record even if data not exist. How to do this?

解决方案

I won't say much about efficiency as I have not tested it against other methods but without having a temp table this seem a fair way to go.

SELECT COUNT(u.userID) AS total, m.month FROM ( SELECT 'Jan' AS MONTH UNION SELECT 'Feb' AS MONTH UNION SELECT 'Mar' AS MONTH UNION SELECT 'Apr' AS MONTH UNION SELECT 'May' AS MONTH UNION SELECT 'Jun' AS MONTH UNION SELECT 'Jul' AS MONTH UNION SELECT 'Aug' AS MONTH UNION SELECT 'Sep' AS MONTH UNION SELECT 'Oct' AS MONTH UNION SELECT 'Nov' AS MONTH UNION SELECT 'Dec' AS MONTH ) AS m LEFT JOIN users u ON MONTH(STR_TO_DATE(CONCAT(m.month, ' 2013'),'%M %Y')) = MONTH(u.userRegistredDate) AND YEAR(u.userRegistredDate) = '2013' GROUP BY m.month ORDER BY 1+1;

If you make the union based on a date format you can even reduce the work and load on the query.

SELECT COUNT(u.userID) AS total, DATE_FORMAT(merge_date,'%b') AS month, YEAR(m.merge_date) AS year FROM ( SELECT '2013-01-01' AS merge_date UNION SELECT '2013-02-01' AS merge_date UNION SELECT '2013-03-01' AS merge_date UNION SELECT '2013-04-01' AS merge_date UNION SELECT '2013-05-01' AS merge_date UNION SELECT '2013-06-01' AS merge_date UNION SELECT '2013-07-01' AS merge_date UNION SELECT '2013-08-01' AS merge_date UNION SELECT '2013-09-01' AS merge_date UNION SELECT '2013-10-01' AS merge_date UNION SELECT '2013-11-01' AS merge_date UNION SELECT '2013-12-01' AS merge_date ) AS m LEFT JOIN users u ON MONTH(m.merge_date) = MONTH(u.userRegistredDate) AND YEAR(m.merge_date) = YEAR(u.userRegistredDate) GROUP BY m.merge_date ORDER BY 1+1;

Live DEMO of both queries.