Mysql 查询获取最近 6 个月的计数，包括计数 0

Question

我需要获取一个列表，其中包含过去 6 个月中每月的人数， 如何强制查询提供 count = 0 的月份？像这样:

table A 
-----------------------------
id |    name    |  created   | 
-----------------------------
1  |    mark    |'2014-10-01'|
2  |    peter   |'2014-10-02'|
3  |    Roger   |'2014-10-03'|
4  |    John    |'2014-09-02'|
5  |    moyes   |'2014-09-03'|
6  |    david   |'2014-08-04'|

我需要得到的结果:

  ----------------------------
  MONTHS  |  YEARS  | TOTAL  |
  ----------------------------
  January |  2015   |  0     |
  December|  2014   |  0     |
  November|  2014   |  0     |
  October |  2014   |  3     |
 September|  2014   |  2     |
  August  |  2014   |  1     |

到目前为止我尝试过的查询: http://sqlfiddle.com/#!2/ef54ce/6

Answer 1

也许，您必须提供包含初始数据报告的虚拟表。 然后，与实际数据结合。为了避免重复数据，您需要使用聚合

SELECT
    m, y, MAX(v) v
FROM
    (
        SELECT 
            DATE_FORMAT('2014-01-01', '%M') as m,
            DATE_FORMAT('2014-01-01', '%Y') as y,
            0 as v
        UNION

        SELECT 
            DATE_FORMAT('2014-02-01', '%M') as m,
            DATE_FORMAT('2014-02-01', '%Y') as y,
            0 as v
        UNION

        .... until December ...

        UNION
        SELECT 
            DATE_FORMAT(created, '%M') as m,
            DATE_FORMAT(created, '%Y') as y,
            COUNT(1) as v
        FROM your_table
        GROUP BY DATE_FORMAT(created, '%Y-%M')
    ) t
GROUP BY y, m
... adjust result ...