Re: Database schema for univesal usage

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Fri, 27 May 2005 08:57:44 +0200
Message-ID: <4296c4e9$1$159$e4fe514c@news.xs4all.nl>

Kenneth Downs wrote:
> David Cressey wrote:
>

>>I've never been able to understand why people say it costs lots of $$$ to
>>add a column to a table.
>>
>>The addition ALTER TABLE ... ADD COLUMN is straight forward.  
>>The fallout on existing queries should be minimal.
>>Getting rid of NULLS in the new column
>>is a data issue,  not a technology issue.
>>
>>Updating INSERTS and UPDATES to the table will take a little work,  but
>>its' no big deal. 
>>Where do the $$$ go?

>
> My goodness. My goodness indeed.
>
> The ALTER TABLE takes a moment, sure, especially if you are working alone,
> don't have any programs making use of the column, and have no users who
> tend to dislike bringing the system down for changes.

Somehow two comparisons get mixed:
Comparison one: implementing a change of requirements without the use of a column addition (scenario 1) versus implementing the same change with "ALTER TABLE .."(2). Comparison two: implementing a change of requirements with the use of a column addition(2) versus not implementing that change (0).

Clearly (0) should be the most expensive scenario or there would be no business case for the change to begin with. IMHO it only makes sence to asess the cost of (2) in relation to (1). The question becomes: How can (2) cost more than (1)?

(0) No change
(1) Realizing the change with only app-deltas
(2) Realizing the change with both "ALTER TABLE" and (less / simpler 

than in 1) app-deltas

> And if you don't have to write down why you did it, or justify it to
> anybody, it's much easier than if you do. Who needs documentation, we can
> all remember, right?

(2) needs less documentation effort than (1)

(snip rant) Received on Fri May 27 2005 - 01:57:44 CDT