Path: utzoo!dciem!nrcaer!sce!cognos!nigelc From: nigelc@cognos.UUCP (Nigel Campbell) Newsgroups: comp.databases Subject: Re: Views (was Re: Database design) Message-ID: <8753@cognos.UUCP> Date: 1 Sep 90 02:59:28 GMT References: <1990Aug21.182201.10707@oracle.com> <1990Aug25.213536.17280@oracle.com> Reply-To: nigelc@cognos.UUCP (Nigel Campbell) Distribution: comp Organization: Cognos Inc., Ottawa, Canada Lines: 48 In article <1990Aug25.213536.17280@oracle.com> mfriedma@oracle.UUCP (Michael Friedman) writes: >In article cimshop!davidm@uunet.UU.NET (David S. Masterson) writes: >>In article <1990Aug21.182201.10707@oracle.com> mfriedma@oracle.com >>(Michael Friedman) writes: > >> Don't bother messing with views. > >>This seems to be a general statement within the community. Why hasn't more >>emphasis been put on "views" as a mechanism for increasing the insulation >>between and application program and the database design? Isn't this what the >>model of views was to support? > >Hey, this isn't fair. I was responding to a particular problem. The >person who posted was making an inappropriate use of views to solve a >problem in an extremely awkward manner. I would never tell someone to >avoid views in general. 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