Re: Do we really need NULL??
From: Richard D Holowczak <holowcza_at_andromeda.rutgers.edu>
Date: 12 Nov 1994 16:44:19 -0500
Message-ID: <3a3cvj$abp_at_andromeda.rutgers.edu>
Date: 12 Nov 1994 16:44:19 -0500
Message-ID: <3a3cvj$abp_at_andromeda.rutgers.edu>
How about this: I have 30 students in a class and 29 of them take the final exam but one needs to take a make-up exam. Do I enter a grade for now ? If so, what grade? If, before the make up someone would like to know the class average, what is the result ?
As previously noted, NULL typically means "No Data".
It is converting this "data" into "information" that is difficult. With NULL, one has no way of knowing the reason the value could not be assigned, hence its ambiguity.
I beleive Joe Celko, a columnist in DBMS
magazine has written a few columns about the
use of NULLs. Perhaps check out some
back issues.
Rich Holowczak
Rutgers University
holowcza_at_andromeda.rutgers.edu
Received on Sat Nov 12 1994 - 22:44:19 CET