Re: select statement fails

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Andrus" <kobruleht2(at)hot(dot)ee>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: select statement fails
Date: 2008-04-10 15:57:25
Message-ID: 2560.1207843045@sss.pgh.pa.us
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"Andrus" <kobruleht2(at)hot(dot)ee> writes:
> 1. SQL assumes that CHARACTER(n) column is always padded with spaces in
> right.
> So casting to text should preserve spaces.

No, it should not. In CHAR(n), trailing spaces are semantically
insignificant; 'foo' and 'foo ' are considered equal. In TEXT
they are just as significant as any other character, and those strings
are definitely not equal. So 'foo ' as CHAR(4) and 'foo ' as TEXT
do not actually mean the same thing at all, and similarly ' ' means
two different things as CHAR(1) and as TEXT, even though they look
the same.

The SQL spec's definition of CHAR(n) behavior is really pretty broken
in my opinion; you're almost always better off using varchar. In this
particular case, where you think that a space has semantic significance,
CHAR(n) is simply wrong.

regards, tom lane

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