From: | Joe Koenig <joe(at)jwebmedia(dot)com> |
---|---|
To: | "SHELTON,MICHAEL (Non-HP-Boise,ex1)" <michael_shelton(at)non(dot)hp(dot)com> |
Cc: | "'pgsql-general(at)postgresql(dot)org'" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Way to use count() and LIMIT? |
Date: | 2001-12-18 21:28:30 |
Message-ID: | 3C1FB4FF.7B8F1FF@jwebmedia.com |
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Thread: | |
Lists: | pgsql-general |
I was currently using a LIMIT and OFFSET to move through 20 at a time. I
need to know the total for 2 reasons:
1) To display it to the user
2) So my script knows whether or not to put a next button.
I was hoping I could avoid 2 queries. Is the best way to do this to just
use LIMIT and OFFSET in one query and just do a count() in the first?
Does using a cursor offer any benefit over the LIMIT and OFFSET method? Thanks,
Joe
"SHELTON,MICHAEL (Non-HP-Boise,ex1)" wrote:
>
> You will also need to do a select first to get the total count. You can
> store it in a var then pass it back to the user for each 20 or whatever
> amount (so each time they know total) or pass it once, then create cursor.
>
> You can also use LIMIT with OFFSET to do a simple select each time for 20 at
> a time.
>
> -----Original Message-----
> From: Jason Earl [mailto:jason(dot)earl(at)simplot(dot)com]
> Sent: Tuesday, December 18, 2001 12:27 PM
> To: joe(at)jwebmedia(dot)com
> Cc: pgsql-general(at)postgresql(dot)org
> Subject: Re: [GENERAL] Way to use count() and LIMIT?
>
> Sure, just declare a cursor. Here's a simple one that I use:
>
> DECLARE raw_data CURSOR FOR
> SELECT
> (SELECT pc FROM curpack1 WHERE curpack1.dt <= caseweights1.dt
> ORDER BY curpack1.dt DESC LIMIT 1) AS "pc",
> dt::date AS "date",
> dt::time AS "time",
> weight AS "weight"
> FROM caseweights1
> WHERE dt >= '%s' AND
> dt < '%s'
> ORDER BY dt;
>
> Then you simply fetch from this cursor (like so):
>
> FETCH FORWARD 20 IN raw_data;
>
> And you close it with a simple:
>
> CLOSE raw_data;
>
> Jason
>
> Joe Koenig <joe(at)jwebmedia(dot)com> writes:
>
> > Is there a way to structure a query so you can only run 1 query, get the
> > full number of rows that would be returned, but then use LIMIT to step
> > through in groups of 20? For example, a search in my CD's/Rock section
> > will return 53,000 results. I want to give the user the number of total
> > results, but also use LIMIT to go through 20 at a time? Does this
> > require 2 queries? Thanks,
> >
> > Joe
> >
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