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Re: Warehousing : Constraints

From: Dusan Bolek <pagesflames_at_usa.net>
Date: 16 Nov 2001 07:06:42 -0800
Message-ID: <1e8276d6.0111160706.5c536073@posting.google.com>


"Billy Verreynne" <vslabs_at_onwe.co.za> wrote in message news:<9t2b0l$5ja$1_at_ctb-nnrp2.saix.net>...
> So the requirement is parent child integrity - a very valid reason (critical
> IMO). However, that can be done without necassarily having to use foreign key
> constraints, though fk constraints are the "best solution" from a pure
> database perspective.

I will add some comments to "my part" of message. You're true, that FK are not the only solution to integrity issues. You can also enforce consistency in application code. However I have very bad experiences with this approach. If you will write code yourself, you can make everything OK, but data warehouses are usually a team project, sometimes even a big team project. Maybe three or more programmers will work on your warehouse, so all depends how these programmers will be good and have a proper discipline. The second requirement is very seldomly fulfilled. If only one of them forgot in some part of code to implement these "SW constraints" or implement them badly, then you will run into big problems. My opinion is that FK constraints are the best solution, becuase they're almost dumbproof.
If you don't want to use them, then you have one more way. You can write your checking scripts to test integrity. I had complex scripts, while clearing shit out of that data warehouse mentioned in my previous post. You must take into account that these scripts sometimes runs for several hours, but data warehouses are only seldomly 24x7 system (typically DWs in multinational corporations), so usually you have a time enough to run them.

--
_________________________________________

Dusan Bolek, Ing.
Oracle team leader

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Received on Fri Nov 16 2001 - 09:06:42 CST

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