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Re: varchar vs char vs text

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Brett W(dot) McCoy" <bmccoy(at)chapelperilous(dot)net>
Cc: Singer Wang <swang(at)cs(dot)dal(dot)ca>, pgsql-novice(at)postgresql(dot)org
Subject: Re: varchar vs char vs text
Date: 2002-02-12 21:45:13
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Lists: pgsql-novice
"Brett W. McCoy" <bmccoy(at)chapelperilous(dot)net> writes:
> I'd go with text.  It's not SQL92, though.


> varchar is technically supposed to have a limit of 255,

Certainly not; the spec says

            The maximum value of <length> is implementation-defined.

There may be implementations that are lame enough to limit it to 255,
but Postgres isn't one of them.  IIRC, we set a rather arbitrary upper
limit of 10000000 on the length (mainly on the theory that anything
larger is either a typo, or you really don't want a limit at all, in
which case you oughta be using text).

At least in 7.2, it also works to say just "varchar" with no length
limit; this is functionally equivalent to "text" except perhaps for
some corner cases involving ambiguous-data-type resolution.  But
this is not SQL-spec-compliant either.

			regards, tom lane

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