我想得到的是統計每個月從一個generate_series和計數的ID在每個月的總和。這個SQL工作在PostgreSQL的9.1:加入postgres中generate_series的計數查詢,也檢索空值爲「0」
SELECT (to_char(serie,'yyyy-mm')) AS year, sum(amount)::int AS eintraege FROM (
SELECT
COUNT(mytable.id) as amount,
generate_series::date as serie
FROM mytable
RIGHT JOIN generate_series(
(SELECT min(date_from) FROM mytable)::date,
(SELECT max(date_from) FROM mytable)::date,
interval '1 day') ON generate_series = date(date_from)
WHERE version = 1
GROUP BY generate_series
) AS foo
GROUP BY Year
ORDER BY Year ASC;
這是我的輸出
"2006-12" | 4
"2007-02" | 1
"2007-03" | 1
但我想是這樣的輸出(一月 「0」 值):
"2006-12" | 4
"2007-01" | 0
"2007-02" | 1
"2007-03" | 1
所以如果有一個沒有ID的月份,它應該被列出。 任何想法如何解決這個問題?
下面是一些樣本數據:
drop table if exists mytable;
create table mytable(id bigint, version smallint, date_from timestamp without time zone);
insert into mytable(id, version, date_from) values
('4084036', '1', '2006-12-22 22:46:35'),
('4084938', '1', '2006-12-23 16:19:13'),
('4084938', '2', '2006-12-23 16:20:23'),
('4084939', '1', '2006-12-23 16:29:14'),
('4084954', '1', '2006-12-23 16:28:28'),
('4250653', '1', '2007-02-12 21:58:53'),
('4250657', '1', '2007-03-12 21:58:53')
;
一如既往,mytable表的定義應該在你的問題中。一些示例值與它會一起膨脹。 –