From: John "Chris" Wren
Date: March 11 1999 9:43pm
Subject: Re: Database Synchronization Methods?
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	For what it's worth, the remote database never changes by any
mechanism other than the system at home pushing records up to it.
The timestamp seems like a good approach to this.

	I'm wondering if SQL supports some "native" method for
synchronizing two databases with identical structures.  As I
mentioned, exporting is a perfectly valid method for what I'm doing,
if I could just get Access to let me overwrite the remote database (I
guess I could issue some SQL statements to drop the tables, then the
export function wouldn't see them.  Just seem cheesy).

	By the way, if you want to see this simplistic little
application in action, it can be found at
www.jcwren.com/cgi-bin/pcpricing.pl

	- John Wren

On Thu, 11 Mar 1999 15:25:31 -0600, you wrote:

>On Thu, 11 Mar 1999 21:19:36 GMT, John "Chris" Wren wrote:
>
>>	Obviously there *has* to be a cleaner and more efficient
>>method than what I'm doing.
>>
>>	What database terminology am I looking for when I do this?
>>Access calls it 'replication', but as near as I can tell, Access only
>>supports replication within Access databases (and they want you to use
>>the stupid 'Briefcase' mechanism).
>
>A common way is to use a time stamp updated with each change.
>
>Look at only records that have changed since last sync, join/link the 2
>versions via the primary key. If the record has changed only in one db,
>make the corresponding change in the other db. If it has changed in
>both, implement some reconciliation scheme (the simplest is to make the
>latest update take precedence).
>
>Probably, you need to lock that databases while you do this to
>distinguish updates made by you in syncing from real updates.
>
>AFAIK, the "briefcase" uses the newest version. Does it really look at
>the data?
>
>
>-Sincerely, Fred
>
>(Frederik Lindberg, Infectious Diseases, WashU, St. Louis, MO, USA)
>
>
>
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---
John "Chris" Wren, KD4DTS
e-mail:   jcwren@stripped / jcwren@stripped
homepage: www.jcwren.com / www.kd4dts.com

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