From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Wei Weng <wweng@kencast.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: select syntax question
Date: Fri, 1 Nov 2002 23:07:04 -0500 (EST)
Message-ID: <200211020407.gA2474Y12040@candle.pha.pa.us> (raw)
In-Reply-To: <1036186412.25294.2.camel@Monet>
Yes, a big difference. The first returns the distinct COUNT values, but
there is only one, of course. The second returns the number of distinct
values in the column.
---------------------------------------------------------------------------
Wei Weng wrote:
> This is what is on postgresql's manual page:
>
> http://www.postgresql.org/idocs/index.php?sql-select.html
>
> SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
> * | expression [ AS output_name ] [, ...]
> [ FROM from_item [, ...] ]
> [ WHERE condition ]
> [ GROUP BY expression [, ...] ]
> [ HAVING condition [, ...] ]
> [ { UNION | INTERSECT | EXCEPT } [ ALL ] select ]
> [ ORDER BY expression [ ASC | DESC | USING operator ] [, ...] ]
> [ FOR UPDATE [ OF tablename [, ...] ] ]
> [ LIMIT { count | ALL } ]
> [ OFFSET start ]
>
> According to this syntax, SELECT DISTINCT COUNT(ID) FROM test
> should be valid while SELECT COUNT(DISTINCT ID) FROM test otherwise.
>
> while in fact, both are valid.
>
> Is there any difference between this two queries?
>
> Thanks!
>
>
> --
> Wei Weng
> Network Software Engineer
> KenCast Inc.
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
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To: pgsql-sql@postgresql.org
Cc: pgman@candle.pha.pa.us, wweng@kencast.com
Subject: Re: select syntax question
In-Reply-To: <200211020407.gA2474Y12040@candle.pha.pa.us>
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