Re: [SQL] Problems with PARTITION BY with count() in window-func

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От	Andreas Joseph Krogh
Тема	Re: [SQL] Problems with PARTITION BY with count() in window-func
Дата	8 ноября 2017 г. 19:50:20
Msg-id	VisenaEmail.47.ec56caa56a402a62.15f9bdc4735@tc7-visena обсуждение исходный текст
Ответ на	[SQL] Problems with PARTITION BY with count() in window-func (Andreas Joseph Krogh <andreas@visena.com>)
Ответы	Re: [SQL] Problems with PARTITION BY with count() in window-func ("MS (direkt)" <martin.stoecker@stb-datenservice.de>)
Список	pgsql-sql

Дерево обсуждения

På onsdag 08. november 2017 kl. 11:17:39, skrev Andreas Joseph Krogh <andreas@visena.com>:

Hi all.

I'm trying to count() all log-entries per activity per month in a separate column using count() over(partition by ...) but get an error I don't understand.
[snip]
select
      date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) AS month
    , log.activity_id   , count(log.entity_id) AS num_logs   , count(log.entity_id) OVER total_for_month_window AS total_for_month
FROM
    log_entry log
WHERE 1 = 1
      AND date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) BETWEEN '2017-01-01'::DATE AND '2017-05-01'::DATE
GROUP BY month, log.activity_id
WINDOW total_for_month_window AS (PARTITION BY date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE))

ORDER BY date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) ASC
;
Note the missing log.entity_id in GROUP BY.

but this gives the error:

[42803] column "log.entity_id" must appear in the GROUP BY clause or be used in an aggregate function
Details

This query gives the desired results:

SELECT DISTINCT
      date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) AS month
    , log.activity_id   , count(log.entity_id) OVER(partition by date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE), log.activity_id) AS num_logs_per_activity   , count(log.entity_id) OVER (partition by date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE)) AS total_for_month
FROM
    log_entry log
ORDER BY date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) ASC, log.activity_id ASC
;

month	activity_id	num_logs_per_activity	total_for_month
2017-01-01 00:00:00.000000	1	2	4
2017-01-01 00:00:00.000000	2	2	4
2017-02-01 00:00:00.000000	1	5	6
2017-02-01 00:00:00.000000	2	1	6

But I'd like a solution without the DISTINCT, if one exists?

If I introduce a new column, logged_for, and want to list number of logged entries per person per activity I can use this:

SELECT DISTINCT
    date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) AS month
    , log.logged_for   , log.activity_id   , count(log.entity_id) OVER(partition by date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE), log.logged_for, log.activity_id) AS num_logs_per_person_for_activity   , count(log.entity_id) OVER (partition by date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE), log.logged_for) AS total_for_person_for_month
FROM
    log_entry log
ORDER BY date_trunc('month', log.start_date::TIMESTAMP WITHOUT TIME ZONE) ASC
;

Which gives:

month	logged_for	activity_id	num_logs_per_person_for_activity	total_for_person_for_month
2017-01-01 00:00:00.000000	5	1	2	4
2017-01-01 00:00:00.000000	5	2	2	4
2017-01-01 00:00:00.000000	6	1	2	4
2017-01-01 00:00:00.000000	6	2	2	4
2017-02-01 00:00:00.000000	5	1	5	6
2017-02-01 00:00:00.000000	5	2	1	6
2017-02-01 00:00:00.000000	6	1	5	6
2017-02-01 00:00:00.000000	6	2	1	6