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From:Paul DuBois Date:January 3 2000 10:16pm
Subject:Re: sequence table: Definitive answer please!
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At 4:17 PM -0500 2000-01-03, Bob Strouper wrote:
>Hello,
>
>I've read and read the manual and posts on the mailing
>list but still have not found the definitive answer on how
>to make a sequence table ( unique counter table ) that
>will definitly give a unique number.  In my situation,
>many procceses will be reading and writing to this sequence
>table *at_the_same_time* and every proccess must read a unique number and
>write a unique number.

It doesn't matter whether or not multiple clients are accessing
the table simultaneously.  The value returned by LAST_INSERT_ID()
is maintained on a per-client (per-connection) basis, and no
client can receive another client's number.


>This is what I am doing at the moment:
>
>CREATE TABLE sequence (
>ID mediumint(12) DEFAULT '0' NOT NULL auto_increment,
>PRIMARY KEY (ID)
>);
>
>...now:
>
>"UPDATE sequence SET id=last_insert_id(id+1)
>"select last_insert_id() as id from sequence";
>
>Will id now be unigue no matter what?

Yes.  See above.

>
>Please help... this is really bending my mind ;-)
>
>Thanks in advance,
>Bob
>
>P.S. I really don't want to give my input in fear of
>confusing things more ;-) but the reason that I think
>that this would break is that every proccess has its
>own last_insert_id...and therefore one last_insert_id
>could be the same as an other :-(

That statement seems self-contradictory to me.  If each
process has its own value, how could one be the same
as another?

-- 
Paul DuBois, paul@stripped
Thread
sequence table: Definitive answer please!Bob Strouper4 Jan
  • Re: sequence table: Definitive answer please!Paul DuBois4 Jan
    • Re: sequence table: Definitive answer please!Paul DuBois4 Jan
  • Re: sequence table: Definitive answer please!Tonu Samuel4 Jan
    • Re: sequence table: Definitive answer please!Benjamin Pflugmann4 Jan
  • Re: sequence table: Definitive answer please!Benjamin Pflugmann4 Jan
  • Re: sequence table: Definitive answer please!hypnos4 Jan
Re: sequence table: Definitive answer please!Bob Strouper4 Jan
  • Re: sequence table: Definitive answer please!Paul DuBois4 Jan
  • Re: sequence table: Definitive answer please!Benjamin Pflugmann4 Jan
Re: sequence table: Definitive answer please!Benjamin Pflugmann4 Jan
Re: sequence table: Definitive answer please!Bob Strouper4 Jan
  • Re: sequence table: Definitive answer please!Benjamin Pflugmann4 Jan
Re: sequence table: Definitive answer please!Bob Strouper4 Jan