RE: time/date as key fields

I've started with new applications. Makes writing sql select statements a lot easier since I only need to join on one field.

But in a current project I'm looking to create a unique key on file created with DDS. The file in DDS was created with a unique key on Company and Product. However, SQL doesn't recognize it as a unique key and I cannot use it when creating foreign key constraints link other table to it. So on this file I created a new unique key with the same key fields as the DDS file in the test system. It shouldn't take long to create in production, problem is I think nobody can be accessing the file at the time of the build.

I'm also curious. I'm wanting to create foreign keys from new SQL tables for this new project to this master file. Should be okay to do correct? I'm believing with the foreign key constraint would make gathering data later faster. There would be no for SQL to look for access path between the two because it already exists.





-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Richard Schoen
Sent: Friday, November 19, 2010 9:42 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Re: time/date as key fields

A combination of _GENUUID, Verns timestamp routine and job info would most likely guarantee uniqueness :-)

Otherwise an Identity field in the database indeed guarantees it.

Curiousity question:

How many of you are using Identity fields in databases for new applications ?

In the past we always created the base key such as Customer Number, Order Number and that was the primary key. Now I think the wisdom is to always use an identity field for primary key as well as Customer Number, Order Number, etc.... as indexes.

Would like to hear thoughts ?.....

Regards,
Richard Schoen
RJS Software Systems Inc.
Where Information Meets Innovation
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Email: richard@xxxxxxxxxxxxxxx
Web Site: http://www.rjssoftware.com
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message: 9
date: Fri, 19 Nov 2010 15:07:43 +0100
from: <dieter.bender@xxxxxxxxxxxx>
subject: Re: time/date as key fields

... it depends, maybe for referential constraints, if there are database
relations.
BTW: genUUID on AS/400 is only most likely unique!!! Best choice would be an
identity column, if uniqueness is needed.

D*B