Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!bionet!ames!haven!vrdxhq!bms-at!stuart From: stuart@bms-at.UUCP (Stuart Gathman) Newsgroups: comp.databases Subject: Re: Relational Model Summary: Ordering in relational model Keywords: relational empirical support Message-ID: <172@bms-at.UUCP> Date: 26 Jul 89 18:23:42 GMT References: <18886@sequent.UUCP> <19101@sequent.UUCP> Organization: Business Management Systems, Inc., Fairfax, VA Lines: 14 SQL and 'C' terminology used below: Ordering in a relational system is like 'int' in 'C'. When no order is specified, you get the most efficient order for the implementation. If a specific order is desired, it can be requested. ("SORT BY"). 'INDEX' is an optimization hint to the system, like 'register' in 'C'. One thing in the relational model I disagree with: Duplicate records are useless in any order. All tables should be required to have a "UNIQUE" combination of fields. After all, we are dealing with *sets*, not *bags*. :-) -- Stuart D. Gathman <..!{vrdxhq|daitc}!bms-at!stuart>