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  1. #1
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    Question on Snowflake vs. Star schemas.

    Howdy all. So Im reading a tutorial on designing a Data Warehouse:

    http://freedatawarehouse.com/tutoria...0Tutorial.aspx

    and Im on the page describing Snowflake design:

    http://freedatawarehouse.com/tutoria...%20Schema.aspx

    and it claims: "General rule of thumb is keep away from snow flake schemas as even though they may save you some space, they will cost a lot in terms of query times."

    I'm having a hard time getting my head into this one. Is the only benefit to Snowflake schemas really space savings? There has got to be more than that?

    TIA, CFR

  2. #2
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    G@dd$mn F#&$ing Star Schemas And Snowflakes Are Not Data Warehouses!
    If it's not practically useful, then it's practically useless.

    blindman
    www.chess.com: "sqlblindman"
    www.LobsterShot.blogspot.com

  3. #3
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    Ok, I just went through that "tutorial", and to call it rudimentary would be generous. That site exists solely to link to sponsor sites. You need to find some more reputable and thorough information sources on Data Warehousing. Try any of the books by Bill Inmon.
    If it's not practically useful, then it's practically useless.

    blindman
    www.chess.com: "sqlblindman"
    www.LobsterShot.blogspot.com

  4. #4
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    Quote Originally Posted by blindman
    Ok, I just went through that "tutorial", and to call it rudimentary would be generous. That site exists solely to link to sponsor sites.
    yes, it sure does look awful

    general rule of thumb: if the first thing you see when landing on a page is a bunch of ads, go somewhere else, because that site will waste your time

    and don't click on any of their ads, because then they gotcha

    think about it: if the site's content is any good, people won't click any of the ads, because they'll find what they want, but if the content is crap, then the ads will be more appealing as a possible source of what you're looking for

    and of course, why would someone build a site with ads? hint: it most certainly is not to help you find information
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  5. #5
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    So, I'd say this question went well.

    O.K. so I need to read more than a brief tutorial to be taken seriously, fair enough. From what Im reading, Inmon and Kimball are the main guys out there? Simply put, I dont have time to read a 400-500 page book. Can anyone recommend a happy medium between a banner filled tutorial and something that will take me months to read, let alone digest?
    Last edited by cfr; 10-13-06 at 13:54.

  6. #6
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    Quote Originally Posted by cfr
    Simply put, I dont have time to read a 400-500 page book.
    Uhm...how much time to did you budget to create an Enterprise Data Warehouse?

    Look, a lot of this is going to depend upon your personal experience and skill as a DBA. You should definitely read some material about data warehousing before you get started, and I personally think that Inmon's books do the best job of explaining the concept and philosophy. But one of the key ideas that you will learn is that building a data warehouse is an interative process. It is okay to start small with a few tables focusing on one or two business areas, and then enhance and prune from there. The key thing is to avoid any architecture that limits the ability to modify the data structure. This means making sure that all access to the database goes through views and sprocs rather than directly to tables, along with other best-practices principles. And Inmon's approach is actually more conducive to starting small, because using a 3rd normal form makes it easy to expand the scope of the database.
    What you eventually come to understand is the data warehousing is as much a process as it is an architecture. The policies and procedures you implement to manage the growth and use of the data are what determine whether the project will succeed or fail.
    If it's not practically useful, then it's practically useless.

    blindman
    www.chess.com: "sqlblindman"
    www.LobsterShot.blogspot.com

  7. #7
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    Quote Originally Posted by blindman
    Uhm...how much time to did you budget to create an Enterprise Data Warehouse?
    None. I am doing this on my own. I may need to go get a new job a few months from now and want to increase my skill set.

    Quote Originally Posted by blindman
    Look, a lot of this is going to depend upon your personal experience and skill as a DBA. You should definitely read some material about data warehousing before you get started, and I personally think that Inmon's books do the best job of explaining the concept and philosophy. But one of the key ideas that you will learn is that building a data warehouse is an interative process. It is okay to start small with a few tables focusing on one or two business areas, and then enhance and prune from there. The key thing is to avoid any architecture that limits the ability to modify the data structure. This means making sure that all access to the database goes through views and sprocs rather than directly to tables, along with other best-practices principles. And Inmon's approach is actually more conducive to starting small, because using a 3rd normal form makes it easy to expand the scope of the database.
    What you eventually come to understand is the data warehousing is as much a process as it is an architecture. The policies and procedures you implement to manage the growth and use of the data are what determine whether the project will succeed or fail.
    This in itself is pretty informative, thanks. It would appear that you favor Inmon over Kimball? Out of curiosity, why?

  8. #8
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    I don't have any problem with Kimball's approach to datamarts, and he really pioneered the concept. I have a problem with him calling them data warehouses. Data warehousing initiatives have a reputation for failure, largely because of misconceptions about what they are.
    If you tell your users that you are going to create an enterprise data warehouse and all you give them is a datamart, or a collection of datamarts, the execution is going to fall way short of the expectations. It gives data warehousing a bad name. I think a lot of disreputable data warehouse "professionals" push the star schema solution like snake oil salesmen.

    Bill Inmon: Father of Data Warehousing.
    Ralph Kimball: Father of Data Marts.
    If it's not practically useful, then it's practically useless.

    blindman
    www.chess.com: "sqlblindman"
    www.LobsterShot.blogspot.com

  9. #9
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    Lol - well done cfr - I think you have influenced Blindman's new sig.
    Testimonial:
    pootle flump
    ur codings are working excelent.

  10. #10
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    Quote Originally Posted by pootle flump
    Lol - well done cfr - I think you have influenced Blindman's new sig.

    Hey, I do what I can...

  11. #11
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    Quote Originally Posted by blindman
    I don't have any problem with Kimball's approach to datamarts, and he really pioneered the concept. I have a problem with him calling them data warehouses. Data warehousing initiatives have a reputation for failure, largely because of misconceptions about what they are.
    If you tell your users that you are going to create an enterprise data warehouse and all you give them is a datamart, or a collection of datamarts, the execution is going to fall way short of the expectations. It gives data warehousing a bad name. I think a lot of disreputable data warehouse "professionals" push the star schema solution like snake oil salesmen.

    Bill Inmon: Father of Data Warehousing.
    Ralph Kimball: Father of Data Marts.
    Any ideas on who is more widely accepted in the industry?

  12. #12
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    what is this, a popularity contest? the cult of personality?

    my advice: design what makes sense for you and for your organization
    rudy.ca | @rudydotca
    Buy my SitePoint book: Simply SQL

  13. #13
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    Quote Originally Posted by r937
    what is this, a popularity contest? the cult of personality?

    my advice: design what makes sense for you and for your organization

    My organization isnt doing any anything like this, and I am teaching this to myself purely to advance my skill set.

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