Re: subtract a day from the NOW function

From: Michael Glaesemann <grzm(at)seespotcode(dot)net>
To: "Fernando Hevia" <fhevia(at)ip-tel(dot)com(dot)ar>
Cc: <pgsql-sql(at)postgresql(dot)org>
Subject: Re: subtract a day from the NOW function
Date: 2007-06-07 21:53:03
Message-ID: 7719EE57-A3BA-4301-9C94-B4FD5DBA3FCB@seespotcode.net
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On Jun 7, 2007, at 15:38 , Fernando Hevia wrote:

> Why not? I'm curious if has anything to do with performance or just
> style?

Not style. Maybe performance because there's fewer function calls,
but primarily correctness. By using to_char you no longer have a date—
you have a text value—and are relying on the collocation of your
database to compare two text values. This can lead to subtle bugs in
your code. Similarly, I would never use to_char to compare two integers:

SELECT 20 > 9 AS int_values
, to_char(20, '9') > to_char(9, '9') AS text_values;

Is this what you would expect? What's the advantage to using to_char?

Michael Glaesemann
grzm seespotcode net

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