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Message Posted: Fri, 02 Nov 2001 @ 13:04:04 GMT
My experience has been that while these tools do not always generate the most efficient SQL code/queries in all instances, 3NF is not significantly different than a starish model on a pure performance basis all else being equal (which is difficult to achieve!). I will say however that Teradata's architecture can allow a given schema to perform where you might have more trouble getting equal performance out of that same schema running on a non-Teradata platform.
In my view, it is the understanding/knowledge that the end users have about the business data and its structure that makes the determining factor. Stars, snowflakes and schemas of their like can be complex or simple. A 3NF schema can be complex or simple. Generally (and this is a big generalization) I find that star schemas tend to be a little less complex for business users/non-modelers to grasp as the business rules for relating data items to one another is a little more intuitive/clearly shown. The OLAP tool tie in/generalization is that this tends to be a more straight forward environment to operate in for the tool and well as the user.
A 3NF schema for the same business data generally will be a little more complex (most likely expressed in the terms of the total number of tables and more relationships) but might be a little more flexible in terms of the ways users can breakdown the data and to evolving business needs. Queries in 3NF schemas tend to be a little more complex on average because of the need to join more tables (this is a generalization also). This translates into a little more complexity as a rule, that the users/tools have to be able to handle.
My musings....for what its worth.....Neil
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