MySQL Query with count and group by

问题

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.

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

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

but, it did not work.

回答1:

Assuming that your date is an actual datetime column:

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

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

To find months where there are no records, you will need a date table. If you can't create one, you can UNION ALL a calendar table like so:

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

See a demo

来源：https://stackoverflow.com/questions/14344810/mysql-query-with-count-and-group-by

标签

mysql

count

group-by