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Difference between star schema and snow flake schema design?

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Last Modified: 2012-05-06
Hi Can anyone tell me the difference between star schema and snow flake schema design and if appropriate which is applicable with Data warehousing?

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Snowflake schema architecture is a more complex variation of a star schema design. The main difference is that dimensional tables in a snowflake schema are normalized, so they have a typical relational database design.

Snowflake schemas are generally used when a dimensional table becomes very big and when a star schema cant represent the complexity of a data structure. For example if a PRODUCT dimension table contains millions of rows, the use of snowflake schemas should significantly improve performance by moving out some data to other table (with BRANDS for instance).

The problem is that the more normalized the dimension table is, the more complicated SQL joins must be issued to query them. This is because in order for a query to be answered, many tables need to be joined and aggregates generated.

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Commented:
That...is brillent thanks for you help. The perfect level of detail.
Always ready to help......

Cheers,

Author

Commented:
I am going to raise another question about a beginners guide to data warehouse design if you are interested.

Cheers
I recommend closing this question and opening another one........

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