Re: NULLs: theoretical problems?
Date: Fri, 24 Aug 2007 09:38:41 +0200
Quoth Keith H Duggar:
> So it's required to "write DEF" for all nullable attributes and a
> formula is true only if the nullable attributes are defined. How
> is this different from dropping the requirement to "write DEF" and
> simply defining that a formula is false if any of it's variables
> is undefined? And how is that different from allowing NULL and
> defining that a formula is false if any variable is NULL?
Note that SQL does not actually do this, and Jan Hidder's example depends on it. TRUE OR NULL is TRUE, not NULL (or FALSE). Would you have it otherwise?
-- JonReceived on Fri Aug 24 2007 - 09:38:41 CEST