A long time ago, in a galaxy far, far away, tshipley@xxxxxxxx (Trent Shipley) wrote: > On Thursday 2006-06-08 15:14, David Fetter wrote: >> On Thu, Jun 08, 2006 at 05:21:07AM -0700, dananrg@xxxxxxxxx wrote: > >> on bag theory[1] and 3-value logic[2]. Until they come up with a >> testable system, or Hell freezes over, whichever comes first, >> Pascal's book will make a good companion on your shelf to books on >> Phlogiston[3] theory, or a decent doorstop, whichever you prefer. > > I have encountered at least two commercial database products that > declared every column "NOT NULL". I have always assumed that this > was defensive, preventing stupid programmer mistakes. > > I recall reading somewhere that Codd proposed multiple flavors of > nullity. Are there theoretical proposals for databases with logical > systems having more than three values? Darwen did a paper where he described how you'd cope with not having any nulls. It amounted to having a whole bunch of views that would have a whole host of special indicator values to replace the multiple meanings of NULL... -- let name="cbbrowne" and tld="gmail.com" in String.concat "@" [name;tld];; http://linuxdatabases.info/info/lisp.html Including a destination in the CC list that will cause the recipients' mailer to blow out is a good way to stifle dissent. -- from the Symbolics Guidelines for Sending Mail
