Re: unexpected join results - Mailing list pgsql-general
From | Dann Corbit |
---|---|
Subject | Re: unexpected join results |
Date | |
Msg-id | D90A5A6C612A39408103E6ECDD77B829408A97@voyager.corporate.connx.com Whole thread Raw |
In response to | unexpected join results (Matthew Phillips <mphillips@timing.com>) |
List | pgsql-general |
-----Original Message----- From: Matthew Phillips [mailto:mphillips@timing.com] Sent: Tuesday, March 18, 2003 10:28 AM To: pgsql-general@postgresql.org Subject: [GENERAL] unexpected join results Here is my problem in the most abstract way I can convey it... I am doing a simple join on two tables. The query: select m.source_id, second, begin_time, end_time from measurements m, measurement_list l where m.source_id = l.source_id and m.second > l.begin_time and l.end_time IS NOT NULL; produces the output: source_id | second | begin_time | end_time -----------+---------------------+---------------------+---------------- ----- 2 | 2003-03-18 10:09:45 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:46 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:47 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:48 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:49 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:50 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:51 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:52 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:53 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:54 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:55 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:56 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:57 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:58 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:09:59 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:00 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:01 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:02 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:03 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:04 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:05 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:06 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 2 | 2003-03-18 10:10:07 | 2003-02-18 10:09:06 | 2003-02-18 10:10:03 (23 rows) source_id is an integer identifier, the rest of the columns are timestamp without time zone. This output is expected and perfectly ok... the problem is when I add one more condition to the query. 'and m.second <= l.end_time'. This would match rows in which second falls in between begin_time and end time, something all the above rows do. but... select m.source_id, second, begin_time, end_time from measurements m, measurement_list l where m.source_id = l.source_id and m.second > l.begin_time and l.end_time IS NOT NULL and m.second <= l.end_time; produces: source_id | second | begin_time | end_time -----------+--------+------------+---------- (0 rows) But I can look back on the previous query results and see that in every row the second is less than the end time! I am not exactly an sql guru, but it seems to me that the output should be identical with the extra line in or out. Any clues as to what is going on here? Please give me a quick fix :-) I have been spinning wheels for half a day on this one. I can post more schema info if that is needed. using 7.3.1 on FreeBSD 4.7 -------------------------------------------------------->> Consider: second=2003-03-18 10:09:45 end_time=2003-02-18 10:10:03 Notice that the month is March for second, and February For end_time. This is true for all the rows. The query Result set is correct. Any time stamp in march of 2003 will be bigger than one in February of 2003. <<--------------------------------------------------------
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