JOIN query not working as expected - Mailing list pgsql-sql

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:

SELECTservices.id AS service_id,(SELECT     COUNT(id)FROM    messagesWHERE    (messages.service_id = services.id)
AND(messages.receiving_time >= '2005-10-01')    AND (messages.receiving_time < '2005-10-30')) AS "count",
services.keyword
FROMservices
WHERE(services.vpn_id = 1)       AND(    (services.start_time IS NULL OR services.start_time <= '2005-10-30')    AND
(services.end_timeIS NULL OR services.end_time >= '2005-10-01'))
 
GROUP BYservices.id,services.keyword
ORDER BYservices.keyword

[this query shows correctly, for service 'cocker', that '"count"' column
has value 0]


I transformed query to this:

SELECTservices.id AS service_id,count(messages.id) as "count",       services.keyword
FROMservicesLEFT OUTER JOIN messages    ON services.id = messages.service_id
WHEREservices.vpn_id = 1AND messages.receiving_time BETWEEN '2005-10-01' AND '2005-10-30'
GROUP BYservices.id,services.keyword
ORDER BYservices.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."