sybperl-l Archive

From: michael dot peppler at bnpparibas dot com
Subject: Re: Probably Trivial: Finding Largest Primary Key used in Table
Date: Jun 30 2005 12:54PM

First of all, a primary key can be a composite value, a string, or some
other value that isn't simply incrementable.

But if you want to limit yourself to tables that have numeric primary keys
then a "select max(keycol) from table" will give you that information.
HOWEVER, this is not a safe method in an environment with fairly high
volume, as the max value is likely to change between the time you fetch the
value and the time you want to insert the next entry.

The usual technique is to use a key table which holds the next available
key value, and get this value in a transaction.

You can read more about this issue at http://www.sybase.com/detail?id=860

Michael




Internet
jay.listo@gmail.com@peppler.org - 30/06/2005 13:16


Sent by:    owner-sybperl-l@peppler.org

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Subject:    Probably Trivial: Finding Largest Primary Key used in Table


Hi All,

This may sound trivial...but I've been trying to find out how to find
the largest primary key that's been assigned/used within a table.

I'm new to DB development while I have done some DBA.

It would save me trouble when I want to keep control of the primary
keys, make sure that when I insert a new record I can assign a unique
primary key.

I would like to do this using a perl script...not as some stored
procedure or constraint so as to keep it as DB independent (regardless
of Sybase, MySQL, Oracle, etc) as possible.

Best Regards,
Jay




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