From: Mario Splivalo <mario.splivalo@mobart.hr>
To: pgsql-sql@postgresql.org
Subject: JOIN query not working as expected
Date: Tue, 06 Dec 2005 15:08:03 +0100
Message-ID: <1133878084.8161.22.camel@ekim> (raw)
How is this possible?
I have two tables. 'services', and 'messages'. Each message can be
assigned to one service, or it can be unnasigned. Therefore 'service_id'
column in table 'messages' is not foreign-keyed to 'id' column in
services table. services.id is PK for services, messages.id is PK for
messages.
Now, here goes:
pulitzer2=# select * from services where id = 1001;
id | keyword | type_id | vpn_id | start_time | end_time
| day_boundary | week_boundary | month_boundary | recurrence |
random_message_count
------+---------+---------+--------+------------+------------------------+--------------+---------------+----------------+------------+----------------------
1001 | cocker | 1 | 1 | | 2005-10-20 12:00:00+02
| | | | 1 |
(1 row)
Ok, I have a service with id 1001 which is called 'cocker'.
Now, I want all the messages for that service within certain period:
pulitzer2=# select * from messages where service_id = 1001 and
receiving_time between '2005-10-01' and '2005-10-30';
id | from | to | receiving_time | raw_text | keyword | destination_id |
vpn_id | service_id | status | reply
----+------+----+----------------+----------+---------+----------------+--------+------------+--------+-------
(0 rows)
Ok, no such messages.
Now I want all services which didn't have any messages within certain
period:
pulitzer2=# select * from services where id not in (select distinct
service_id from messages where receiving_time between '2005-10-01' and
'2005-10-30');
id | keyword | type_id | vpn_id | start_time | end_time | day_boundary
| week_boundary | month_boundary | recurrence | random_message_count
----+---------+---------+--------+------------+----------+--------------+---------------+----------------+------------+----------------------
(0 rows)
Why is that?
I 'discovered' above mentioned when I was transforming this query:
SELECT
services.id AS service_id,
(SELECT
COUNT(id)
FROM
messages
WHERE
(messages.service_id = services.id)
AND (messages.receiving_time >= '2005-10-01')
AND (messages.receiving_time < '2005-10-30')
) AS "count",
services.keyword
FROM
services
WHERE
(services.vpn_id = 1)
AND
(
(services.start_time IS NULL OR services.start_time <= '2005-10-30')
AND
(services.end_time IS NULL OR services.end_time >= '2005-10-01')
)
GROUP BY
services.id,
services.keyword
ORDER BY
services.keyword
[this query shows correctly, for service 'cocker', that '"count"' column
has value 0]
I transformed query to this:
SELECT
services.id AS service_id,
count(messages.id) as "count",
services.keyword
FROM
services
LEFT OUTER JOIN messages
ON services.id = messages.service_id
WHERE
services.vpn_id = 1
AND messages.receiving_time BETWEEN '2005-10-01' AND '2005-10-30'
GROUP BY
services.id,
services.keyword
ORDER BY
services.keyword
This query runs MUCH faster, but it omits the 'cocker' column, as if I
used INNER JOIN.
Any clues? I'm stuck here...
Mike
--
Mario Splivalo
Mob-Art
mario.splivalo@mobart.hr
"I can do it quick, I can do it cheap, I can do it well. Pick any two."
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To: pgsql-sql@postgresql.org
Cc: mario.splivalo@mobart.hr
Subject: Re: JOIN query not working as expected
In-Reply-To: <1133878084.8161.22.camel@ekim>
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