From: Rajesh Kumar Mallah. <mallah@trade-india.com>
To: teknokrat@yahoo.com
To: pgsql-sql@postgresql.org
Subject: Re: Can this be done with sql?
Date: Thu, 4 Jul 2002 20:20:29 +0530
Message-ID: <200207042020.29657.mallah@trade-india.com> (raw)
In-Reply-To: <1cbae208.0207031032.7d1be1a2@posting.google.com>
References: <1cbae208.0207031032.7d1be1a2@posting.google.com>
Hi ,
you can use GROUP BY , at the expense of adding one more column of SERIAL data type,
say,
select * from t_a limit 10;
access_log=# SELECT * from t_a limit 15;
sno | value
-----+-------
1 | 4533
2 | 2740
3 | 9970
4 | 6445
5 | 2220
6 | 2301
7 | 6847
8 | 5739
9 | 5286
10 | 5556
11 | 9309
12 | 9552
13 | 8589
14 | 5935
15 | 2382
(15 rows)
if you want avg for every third item you can use:
access_log=# SELECT avg(value) from t_a group by (1+(sno-1)/3) limit 5;
avg
-----------------
5747.6666666667
3655.3333333333
5957.3333333333
8139.0000000000
5635.3333333333
(5 rows)
you can replace 3 in the SQL with any number for grouping that many records.
if you need MEAN , STDDEV , MAX, MIN etc you can use approprite AGGREGATE that PGSQL supports
for numbers eg for MAX
access_log=# SELECT MAX(value) from t_a group by (1+(sno-1)/3) limit 5;
max
------
9970
6445
6847
9552
8589
(5 rows)
Regds
MAlz.
On Thursday 04 July 2002 00:02, teknokrat wrote:
> In my database i have values recorded in one minute intervals. I would
> like a query that can get me results for other time intervals. For
> example - return maximum value in each 3 minute interval. Any ideas
> how i can do this with sql? I tried writing a procedure in plsql but i
> am told it does not support tuples as output. I can get the all the
> one minute intervals and process them to get me three minute intervals
> in my application but i would rather not do the expensive call for the
> one minute intervals in the first place due to the large number of
> data. any ideas?
>
> thanks
>
>
>
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--
Rajesh Kumar Mallah,
Project Manager (Development)
Infocom Network Limited, New Delhi
phone: +91(11)6152172 (221) (L) ,9811255597 (M)
Visit http://www.trade-india.com ,
India's Leading B2B eMarketplace.
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To: pgsql-sql@postgresql.org
Cc: mallah@trade-india.com, teknokrat@yahoo.com
Subject: Re: Can this be done with sql?
In-Reply-To: <200207042020.29657.mallah@trade-india.com>
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