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From:Paul DuBois Date:May 26 1999 2:52pm
Subject:Re: SHOW COLUMNS confuses CHAR/VARCHAR
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At 9:47 AM -0500 5/26/99, A. Brandic wrote:
>My view was that if you use a CHAR rather than a VARCHAR, execution of  a
>query is faster.  Is this true, and how much faster?
>I've done some test on a few tables with 15 coulms and 15000 rows (simple
>selects and Joins) and there was a difference.  I guess on bigger DBs the
>difference will be greter?  Am I right (or left:)).

I'm not really sure.  But you should be able to keep your table from
turning into a varible length table by creating it like this:

create table Tab1 (
  Code CHAR(8),
  Bank CHAR(40),
  Method CHAR(2),
  Name CHAR(40)
);

That way, you won't have any VARCHAR columns, and MySQL won't mess
with your definition. :-)


>
>Ajdin
>
>
>On Wed, 26 May 1999, Paul DuBois wrote:
>
>> At 8:49 AM -0500 5/26/99, kai@stripped wrote:
>> >>Description:
>> >The output of a
>> >  show columns from TABLE
>> >command has problems with CHAR and VARCHAR columns. The script in the next
>> >section produces the following output:
>> >
>> >Field	Type	Null	Key	Default	Extra
>> >Code	varchar(8)	YES		NULL
>> >Bank	varchar(40)	YES		NULL
>> >Method	char(2)	YES		NULL
>> >Name	varchar(40)	YES		NULL
>> >
>> >Each VARCHAR column was created as a CHAR column, and the CHAR column was
>> >created as a VARCHAR column.
>> >
>> >>How-To-Repeat:
>> >Execute the following script:
>> >
>> >#!/bin/bash
>> >set +x
>> >
>> >mysql -u root <<EOF
>> >
>> >drop database if exists bug;
>> >create database bug;
>> >use bug;
>> >
>> >create table Tab1 (
>> >  Code CHAR(8),
>> >  Bank CHAR(40),
>> >  Method VARCHAR(2),
>> >  Name CHAR(40)
>> >);
>> >
>> >show columns from Tab1;
>> >EOF
>> >
>> >>Fix:
>> >	???
>>
>>
>> MySQL silently changes CHAR(N) to VARCHAR(N) for N>=4 if you have any
>>VARCHAR
>> columns since by including such columns in your table, the records become
>> variable-length anyway.
>>
>> Reference:
>>
>>http://www.mysql.com/Manual_chapter/manual_Reference.html#Silent_column_changes
>>>>
>> --
>> Paul DuBois, paul@stripped
>> Northern League Chronicles: http://www.snake.net/nl/
>>
>> ---------------------------------------------------------------------
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--
Paul DuBois, paul@stripped
Northern League Chronicles: http://www.snake.net/nl/
Thread
SHOW COLUMNS confuses CHAR/VARCHARkai26 May
  • Re: SHOW COLUMNS confuses CHAR/VARCHARPaul DuBois26 May
    • Re: SHOW COLUMNS confuses CHAR/VARCHARA. Brandic26 May
      • Re: SHOW COLUMNS confuses CHAR/VARCHARPaul DuBois26 May
        • Re: SHOW COLUMNS confuses CHAR/VARCHARA. Brandic26 May