From: | Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> |
---|---|
To: | Oliver Smith <oliver(at)kfs(dot)org> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Date operations |
Date: | 1999-03-31 16:19:54 |
Message-ID: | 37024B2A.541B46AA@alumni.caltech.edu |
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Thread: | |
Lists: | pgsql-hackers |
> Question 1:
> SELECT COUNT(bytes), SUM(bytes)
> FROM tbl_robot_log
> WHERE email = '$email' AND action = 'sent'
> AND at >= datetime('now' + reltime('-60 mins'::timespan));
> When is the datetime(...) expression evaluated?
The function calls are probably evaluated once per query. And you can
simplify your query a bit:
AND at >= ('now'::datetime + '-60 mins'::timespan);
> Question 2:
> What would be the most efficient way to get the combination of
> 1 and 24 hour logs? Should I get all entries within the last 24
> hours and use a 'group by' statement? If so; how would I do the
> group by? Is there a way to say :
> GROUP BY age(at, 'hours')?
The function you want is date_part('hours', at). Not sure if the GROUP
BY would be happy with it, but istm that you might be able to select a
column of date_part() and then group on that...
- Tom
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