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From:Paul DuBois Date:February 9 2001 2:27am
Subject:Re: auto_increment
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At 4:00 PM -0500 2/8/01, Paul E. Miller wrote:
>I encountered something really handy while playing
>around with mysql.  The documented behavior for
>auto_increment is that it uses the next highest number no
>matter what.
>
>I noticed though, when I have a two element primary key,
>that the auto_increment behavies in a majik uber-cool way.
>I want to use this new found majik, but I'm afraid that
>since it's not documented I won't be able to rely on it in
>future versions.
>
>Is it here to stay?

Yes, it was added in version 3.23.5.  You've discovered the meaning of
this item in the 3.23.5 change notes:

@item
One can now with MyISAM have the auto_increment part as a sub part:
@code{CREATE TABLE foo (a int not null auto_increment, b char(5), 
primary key (b
,a))}

Just make sure the AUTO_INCREMENT column is the last column of the index.

>
>     Example:
>
>     CREATE temporary TABLE neato (
>       type smallint unsigned not null,
>       id   smallint unsigned not null auto_increment,
>
>       PRIMARY KEY (type, id)
>     );
>
>     insert into neato(type)
>         values (1), (1), (1), (2), (2), (2), (2);
>
>     select * from neato;
>
>     +------+----+
>     | type | id |
>     +------+----+
>     |    1 |  1 |
>     |    1 |  2 |
>     |    1 |  3 |
>     |    2 |  1 |
>     |    2 |  2 |
>     |    2 |  3 |
>     |    2 |  4 |
>     +------+----+
>     7 rows in set (0.19 sec)
>
>Will it do this in the future? or just in the version I
>have?


-- 
Paul DuBois, paul@stripped
Thread
auto_incrementPaul E. Miller8 Feb
  • RE: auto_incrementRoger Retamoza8 Feb
  • Re: auto_incrementPaul DuBois9 Feb