6

我写了一个查询来获取用户表中的每月记录，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。这个怎么做？

4

2 回答 2

14

关于效率我不会说太多，因为我没有针对其他方法对其进行测试，但是没有临时表，这似乎是一个公平的方法。

   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;

如果您根据日期格式进行联合，您甚至可以减少查询的工作和负载。

   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。

于 2013-07-29T05:24:03.127 回答
2

您可能需要一个表格来保存每个“月”记录。临时表可以解决问题：

drop table if extists temp_months;
create temporary table temp_months
    month date,
    index idx_date(month);
insert into temp_months
    values ('2013-01-31'), ('2013-02-28'), ...

现在，您可以将您的数据与这个新创建的临时表连接起来：

SELECT 
    COUNT( `userID` ) AS total, 
    DATE_FORMAT( m.month , '%b' ) AS
    MONTH , 
    YEAR( m.month ) AS year
FROM 
    months as m
    left join `users` as u on m.month = last_day(FROM_UNIXTIME(`userRegistredDate`, '%b' )
GROUP BY 
    last_day(m.month);

请注意，您可以将临时表的创建（和填充）放在存储过程中。

为了简单起见，我使用它last_day，但如果您正确加入，您可以自由使用您喜欢的月份中的任何日期。

希望这可以帮助

于 2013-07-29T05:04:48.627 回答