Path: utzoo!attcan!uunet!cimshop!davidm From: cimshop!davidm@uunet.UU.NET (David S. Masterson) Newsgroups: comp.databases Subject: Re: Outerjoin implementation? Message-ID: Date: 19 Sep 90 17:09:15 GMT References: <5803@plains.NoDak.edu> Sender: davidm@cimshop.UUCP Distribution: comp Organization: Consilium Inc., Mountain View, California. Lines: 20 In-reply-to: pcg@cs.aber.ac.uk's message of 18 Sep 90 18:20:04 GMT In article pcg@cs.aber.ac.uk (Piercarlo Grandi) writes: It may be preferable to avoid the difficult issues posed by null values, and the definition of an outer join operation, by attaching instead to each relation (or to the underlying domains) a default value chosen by the schema designer, and/or to make an outerjoin just a join where a suitable matching default value is automatically supplied. This method *may* obviate the need for null records that occur in outer joins, but it doesn't obviate the need for NULLs as attribute values. In fact, this is the method documented by Ingres for doing outer joins in Quel. Using default values, though, has always had the problem of finding a default value that will *never* be used as a live value. -- ==================================================================== David Masterson Consilium, Inc. uunet!cimshop!davidm Mtn. View, CA 94043 ==================================================================== "If someone thinks they know what I said, then I didn't say it!"