Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!shelby!neon!eclipse!ark From: ark@eclipse.stanford.edu (Arthur Keller) Newsgroups: comp.databases Subject: Re: Views (was Re: Database design) Message-ID: <1990Sep12.222410.24946@Neon.Stanford.EDU> Date: 12 Sep 90 22:24:10 GMT References: <1990Aug25.213536.17280@oracle.com> <8753@cognos.UUCP> Sender: news@Neon.Stanford.EDU (USENET News System) Distribution: comp Organization: Stanford University Lines: 42 In article <8753@cognos.UUCP> nigelc@cognos.UUCP (Nigel Campbell) writes: > >I would assume that most people do not create trivial views and discover >very quickly that many are not updateable . As I responded before there >are database systems (Starbase,Interbase possibly Rdb/Vms3.1/4.0) which through >triggers make complex views updateable . However read only views are still >very useful especially if the end-user is given ad-hoc reporting as he >deals in the higher level entities (i.e. the view) not the physical >implementation of an entity exploded into various atomic entities . >Views also help satisfy the need to enforce security by value . > >In fact many Starbase/Rdb/Dg-Sql systems we have built have used views >extensively to great effect > > programs are simpler to write/maintain - reduction in project costs > > programming errors are reduced - ditto also program specs can be more > high level thus allowing the designer > to spend more time refining the design > logically and physically > >I have helped sites with applications where they experienced bad performance >problems where views consisted of views and thus they went back to accessing >the underlying tables directly . Not being a database internals guru I am >not sure of what hurdles optimisers have to cross when determining the >best strategy for such situations , would anyone like to comment on this ? > > >-- >Nigel Campbell Voice: (613) 783-6828 P.O. Box 9707 >Cognos Incorporated FAX: (613) 738-0002 3755 Riverside Dr. >uucp: nigelc@cognos.uucp || uunet!mitel!sce!cognos!nigelc Ottawa, Ontario > CANADA K1G 3Z4 Five years ago, I wrote a dissertation on how to update relational databases through views (actually, a large class of select, project, and join views). If anyone is interested, I could email out a list of references. It may also be possible to send out a collection of reprints, if demand isn't too high. Arthur