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Re: VARCHAR2 vs. CHAR

From: John P. Higgins <jh33378nospam_at_deere.com>
Date: 1997/12/10
Message-ID: <348F455E.3BC4@deere.com>#1/1

How about indexes? I have heard that Oracle works better when the indexed column(s) are char rather than varchar2. I don't know what was meant by 'better'.

John

Thomas Kyte wrote:
>
> A varchar2 field is stored as a data field with a leading length inidicator of
> either 1 or 2 bytes (depending on the string length) and the data. So, a
> varchar2(30) with 10 characters in it will take 11 bytes.
>
> A char fields is stored as a data field with a leading length inidicator or 1 or
> 2 bytes (depending on string length - O8 lets chars be 2000 bytes) and the data
> BLANK PADDED out to the maximum length. So a char(30) will always take either
> zero bytes (null at the end of the row) or 31 bytes.
>
> So a varchar2 is stored varying length and only consumes space for the
> characters in it. A char is always maxed out to the maximum length and consumes
> all of the space.
>
> On Wed, 10 Dec 1997 12:04:18 -0500, "Roy Chang" <roy_chang_at_mail.amsinc.com>
> wrote:
>
> >
> >
> >Hello everbody,
> >
> >I had heard that if I set a field to VARCHAR2(XX), XX being less than 35 or
> >so, that it wouldn't save any space or make a difference. Is this correct?
> >And if so, should I change the fields that are VARCHAR2 and less than 35 to
> >CHAR(XX)?
> >
> >Any comments would be appreciated.
> >
> >Thanks in advance,
> >
> >Roy.
> >
> >
> >
>
>
> Thomas Kyte
> tkyte_at_us.oracle.com
> Oracle Government
> Bethesda MD
>
> http://govt.us.oracle.com/ -- downloadable utilities
>
> ----------------------------------------------------------------------------
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Received on Wed Dec 10 1997 - 00:00:00 CST

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