MySQL查询与计数和分组 [英] MySQL Query with count and group by

问题描述

我有一个表格，其中包含发布商的不同记录，每个记录都有一个类型为时间戳记的日期。

I've got table a table with different records for publishers, each record have a date in a column of type timestamp.

id | id_publisher | date
1           1      11/2012 03:09:40 p.m.
2           1      12/2012 03:09:40 p.m.
3           2      01/2013 03:09:40 p.m.
4           3      01/2013 03:09:40 p.m.
5           4      11/2012 03:09:40 p.m.
6           4      02/2013 03:09:40 p.m.
7           4      02/2012 03:09:40 p.m.

我需要计算每个发布商每个月发布的记录数。例如

I need a count for number of records published by each publisher for each month. For example

Month    |  id_publisher         | num
11/2012  |          1            |   1
11/2012  |          2            |   0
11/2012  |          3            |   0
11/2012  |          4            |   1
.....
02/2013  |          4            |   2

我尝试使用
从raw_occurrence_record组中按月（日期）选择计数，id_publisher;

I tried with select count(id) from raw_occurrence_record group by month(date), id_publisher;

但不起作用。

推荐答案

您的日期是实际的 datetime 列：

SELECT MONTH(date), YEAR(date), id_publisher, COUNT(*)
FROM raw_occurrence_record
GROUP BY MONTH(date), YEAR(date), id_publisher

您可以连接您的月份&年如此：

You can concatenate your month & year like so:

SELECT CONCAT(MONTH(date), '/', YEAR(date)) AS Month, id_publisher, COUNT(*)
FROM raw_occurrence_record
GROUP BY MONTH(date), YEAR(date), id_publisher

b $ b

要查找没有记录的月份，您需要一个日期表。如果您无法创建一个，您可以<$ p $ c> UNION ALL 这样的日历表：

SELECT a.year, a.month, b.id_publisher, COUNT(b.id_publisher) AS num
FROM
  (SELECT 11 AS month, 2012 AS year
   UNION ALL
   SELECT 12, 2012
   UNION ALL
   SELECT 1, 2013
   UNION ALL
   SELECT 2, 2013) a
LEFT JOIN raw_occurence_record b
  ON YEAR(b.date) = a.year AND MONTH(b.date) = a.month
GROUP BY a.year, a.month, b.id_publisher

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