Re: quick FK question
From: Yong Huang <yong321_at_yahoo.com>
Date: Wed, 23 Dec 2009 07:30:58 -0800 (PST)
Message-ID: <765418.19204.qm_at_web80604.mail.mud.yahoo.com>
> As soon as fake value becomes normal business value problems might
> arise. I'd personally better deall with NULLs because this is
> WIDELY understand concept both by developers and DBMSes compared
> to some specific value representing NULL, which is -1 for project1,
> 0 for project2 and 187913267532 for project3.
Date: Wed, 23 Dec 2009 07:30:58 -0800 (PST)
Message-ID: <765418.19204.qm_at_web80604.mail.mud.yahoo.com>
> As soon as fake value becomes normal business value problems might
> arise. I'd personally better deall with NULLs because this is
> WIDELY understand concept both by developers and DBMSes compared
> to some specific value representing NULL, which is -1 for project1,
> 0 for project2 and 187913267532 for project3.
I agree. When I do data modeling, I personally never use a fake value for a simple missing value (as for reason of avoiding outer joins). But if multiple special values are needed in the design, and the developers agree, I could use e.g. -1 for generally unknown, -2 for lost, -3 for ... In this case, a single NULL couldn't satisfy the business need, and an additional column for these special values would be a little too wasteful.
Yong Huang
-- http://www.freelists.org/webpage/oracle-lReceived on Wed Dec 23 2009 - 09:30:58 CST