Scenario:
What is the difference between snow flake and star schema?
Solution:
Star Schema
|
Snow Flake Schema
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The star schema is the simplest data
warehouse scheme.
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Snowflake schema is a more complex data warehouse model than a star
schema.
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In star schema each of the dimensions is
represented in a single table .It should not have any hierarchies between
dims.
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In
snow flake schema at least one hierarchy should exists between dimension
tables.
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It contains a fact table surrounded by
dimension tables. If the dimensions are de-normalized, we say it is a star
schema design.
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It contains a fact table surrounded by dimension tables. If a
dimension is normalized, we say it is a snow flaked design.
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In star schema only one join establishes the
relationship between the fact table and any one of the dimension tables.
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In
snow flake schema since there is relationship between the dimensions tables
it has to do many joins to fetch the data.
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A star schema optimizes the performance by
keeping queries simple and providing fast response time. All the information
about the each level is stored in one row.
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Snowflake schemas normalize dimensions to eliminated redundancy. The
result is more complex queries and reduced query performance.
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It is called a star schema because the diagram
resembles a star.
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It
is called a snowflake schema because the diagram resembles a snowflake.
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Thank you :
- kareem