Re: DWH varchar2(4000)

From: Dave Morgan <>
Date: Wed, 24 Dec 2014 09:16:43 -0700
Message-ID: <>

On 12/24/2014 06:43 AM, Mercadante, Thomas F (ITS) wrote:
> Dave,
> I find this an interesting comment. But I worry about data integrity. If we only allow varchar of 255, or 2000, then what are the possible values of that column? Where is the definition of that column?
> to me, this is the lazy way out - don't perform full analysis of what the business process is and just store everything without a care.

The exception is fixed length fields. Other than that if you waste more than 15 seconds on determining field size you are wasting time and effort. You are also wasting the time and effort of the people who have have to review the code. They have to re-evaluate all the custom sizes and determine why they are custom. And of course full and complete documentation is provided. And of course the modeller is never wrong.

Sorry, tell someone who cares, I have a database to run.

As for analysis, why don't you provide the data and reasons for your judgement that proper analysis was not performed? Just as I have provided the reasons for the choices.

And relying on the database for data validation is not wise. Bad data is entered regardless of field size. Constraints are the last line of defence, not the first.

> Is this a new global approach to database design?

No, it was taught to me in the early 90s as part of a formal Data Modelling course. I am pretty sure it is/was standard practise in the old mainframe databases (IMS? IDMS?, it's been a long time :) It is not database design, it is data modelling.


Dave Morgan
Senior Consultant, 1001111 Alberta Limited
403 399 2442
Received on Wed Dec 24 2014 - 17:16:43 CET

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