From: | Jochen Erwied <jochen(at)pgsql-performance(dot)erwied(dot)eu> |
---|---|
To: | Dave Crooke <dcrooke(at)gmail(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Possible parser bug? .... Re: Picking out the most recent row using a time stamp column |
Date: | 2011-02-25 00:03:12 |
Message-ID: | 1923741490.20110225010312@erwied.eu |
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Thread: | |
Lists: | pgsql-performance |
Friday, February 25, 2011, 12:53:08 AM you wrote:
> select distinct on (a, b, c)
> a, b c, time_stamp, value
Without the comma, you declare 'b AS c'
> from data
> order by a, b, c, time_stamp desc;
> The output produced is the same as this query:
> select distinct on (a, b)
> a, b, time_stamp, value
> from data
> order by a, b, time_stamp desc;
the 'c' is optimized away, since it is an alias for b, and thus redundant
for the distinct.
> Not sure if this is considered a parser bug or not, but it feels slightly
> odd not to get an error.
No error, just plain SQL :-)
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Jochen Erwied | home: jochen(at)erwied(dot)eu +49-208-38800-18, FAX: -19
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