RE: Warehouse design: snowflake vs star schemas

Peter - I wouldn't even presume to pass judgements on two such titans of their respective industries, but taking it down a notch, here is what I would make of their discussion.

    The relational model has been extremely powerful, based as it is on a firm mathematical foundation. I would count Chris Date (and I have copies on nearly all his books) as a foremost leader of this field.

    Along comes these data warehousing people, storing their data in a relational database. But they are deliberately flouting the carefully worked out "Rules of Data Normalization" (reading the chart on my wall). Claiming this as a necessary extenuating situation. Opportunities for confusion abound.

    If you think this disagreement is difficult to understand, just try comprehending the disagreements between the two data warehousing leaders, Bill Inmon and Ralph.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Monday, October 14, 2002 10:39 AM
To: Multiple recipients of list ORACLE-L

No no - it wasn't to do with the specifics of snowstorms or cosmic radiation, rather a further discussion of the issues of database design, which ultimately has to be the reference point in any discussion of star schemas etc.

peter

> -----Original Message-----
> From: DENNIS WILLIAMS [mailto:DWILLIAMS_at_LIFETOUCH.COM]
> Sent: 14 October 2002 15:09
> To: Multiple recipients of list ORACLE-L
> Subject: RE: Warehouse design: snowflake vs star schemas
>
>
> Peter - What does this article have to do with snowflake vs.
> star schema? I
> didn't see where Chris Date was advocating snowflaking.
>
> Dennis Williams
> DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
> -----Original Message-----
> Sent: Monday, October 14, 2002 4:59 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Just for the record (and perhaps to confirm that there are
> always two sides
> to a story). Readers may like to see the article Chris Date
> wrote to Ralph
> Kemball on the subject of business rules and integrity constraints:
>
> http://www.dbdebunk.com/kimball1.htm
>
> peter
> edinburgh
>
>
> > -----Original Message-----
> > From: Alexandre Gorbatchev [mailto:alexandre.gorbatchev_at_avermann.de]
> > Sent: 09 October 2002 15:04
> > To: Multiple recipients of list ORACLE-L
> > Subject: RE: Warehouse design: snowflake vs star schemas
> >
> >
> > Dennis,
> >
> > Thanks for the link. It's a great DW resource.
> > There are not only fundamentals, but some valuable real-life
> > stuff, which is
> > what I need. Live and learn, learn,learn...
> >
> > Regards,
> > Alex
> >
> > -----Original Message-----
> > WILLIAMS
> > Sent: Tuesday, October 08, 2002 7:39 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Alexandre
> > Stephane gave you an excellent reply. If you want to learn
> > more about
> > these DW design issues, I would start by visiting
> > http://www.ralphkimball.com. He is one of the leading figures
> > in the DW
> > field, and has copies of all his articles posted on his site.
> > I would start
> > with the oldest articles because those are where he discusses the
> > fundamentals of data warehousing.
> >
> >
> > Dennis Williams
> > DBA
> > Lifetouch, Inc.
> > dwilliams_at_lifetouch.com
> >
> > -----Original Message-----
> > Sent: Tuesday, October 08, 2002 3:29 AM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > Stéphane,
> >
> > Thanks for response.
> >
> > > I have always discplined myself to use star schema and
> > > never snowflake.
> > Would you mind asking why?
> >
> > > The "Which one is easier to implement and easier ETL
> > > ?" is not a good question as your data model should
> > > not be design for the ETL procecess but only for the
> > > querying.
> > I mean ETL to load data _INTO_ data warehouse. Of course,
> > complexity is
> > mostly determined by sources, but still I'd like to know if
> > there is any
> > general influence by DW's data model.
> >
> > Another question. Is it feasible to make date dimension or
> > just use date
> > column? For example, Oracle Discoverer can work with date
> > columns using
> > hierarchies Y->M->D and similar.
> > What is faster: separate table for date dimension or date column?
> > If I go with date dimension table should I use date column as
> > a foreign key
> > in fact table or use some artificial key?
> >
> > TIA,
> > Alexandre
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.com
> > --
> > Author: Alexandre Gorbatchev
> > INET: alexandre.gorbatchev_at_avermann.de
> >
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Author: Robson, Peter
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