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10-12-06, 18:23
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Registered User
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Join Date: Nov 2004
Posts: 126
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Question on Snowflake vs. Star schemas.
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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
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10-13-06, 10:24
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World Class Flame Warrior
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Join Date: Jun 2003
Location: Ohio
Posts: 11,726
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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"
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10-13-06, 10:43
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World Class Flame Warrior
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Join Date: Jun 2003
Location: Ohio
Posts: 11,726
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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"
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10-13-06, 11:59
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SQL Consultant
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Join Date: Apr 2002
Location: Toronto, Canada
Posts: 19,524
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Quote:
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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.
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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
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10-13-06, 12:48
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Registered User
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Join Date: Nov 2004
Posts: 126
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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?
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Last edited by cfr; 10-13-06 at 12:54.
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10-13-06, 14:28
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World Class Flame Warrior
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Join Date: Jun 2003
Location: Ohio
Posts: 11,726
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Quote:
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Originally Posted by cfr
Simply put, I dont have time to read a 400-500 page book.
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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"
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10-13-06, 15:23
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Registered User
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Join Date: Nov 2004
Posts: 126
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Quote:
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Originally Posted by blindman
Uhm...how much time to did you budget to create an Enterprise Data Warehouse?
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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:
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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.
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This in itself is pretty informative, thanks. It would appear that you favor Inmon over Kimball? Out of curiosity, why?
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10-13-06, 17:19
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World Class Flame Warrior
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Join Date: Jun 2003
Location: Ohio
Posts: 11,726
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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"
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10-14-06, 14:22
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King of Understatement
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Join Date: Feb 2004
Location: One Flump in One Place
Posts: 14,905
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Lol - well done cfr - I think you have influenced Blindman's new sig.
__________________
Testimonial:
Quote:
pootle flump
ur codings are working excelent.
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10-16-06, 13:42
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Registered User
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Join Date: Nov 2004
Posts: 126
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Quote:
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Originally Posted by pootle flump
Lol - well done cfr - I think you have influenced Blindman's new sig.
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Hey, I do what I can... 
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10-16-06, 13:43
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Registered User
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Join Date: Nov 2004
Posts: 126
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Quote:
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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.
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Any ideas on who is more widely accepted in the industry?
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10-16-06, 14:04
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SQL Consultant
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Join Date: Apr 2002
Location: Toronto, Canada
Posts: 19,524
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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
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10-16-06, 14:32
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Registered User
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Join Date: Nov 2004
Posts: 126
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Quote:
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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
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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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