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Which schema is best (Star or Snowflake)?
Hi,
Can you please tell me which schema is best for Fast loading data?
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Dear Muthukumar,
Kindly check the attached image for Star Schema vs Snowflake Schema. I hope this will help you to understand in better way.
For more information, please have a look into listed below similar thread
Re: Star & snowflake schema
Kind regards,
Ishfaque Ahmed

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Hi muthukumar,
Please refer to the page 15 from this document Best Practices for Data Modelling, it's a good reference of the advantages and disadvantages of a snowflake vs a star schema. In my personal opinion, I strongly support the Star Schema model, it provides not only better performance but also it's easier to understand for the user. I also recommend to read some of the Kimball techniques for dimensional modeling.
Hope it helps,
-- Karla

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Dear Muthukumar,
Kindly check the attached image for Star Schema vs Snowflake Schema. I hope this will help you to understand in better way.
For more information, please have a look into listed below similar thread
Re: Star & snowflake schema
Kind regards,
Ishfaque Ahmed

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Hi Muthukumar,
Star Schema is the best loading technique.
Snowflake Schema | Star Schema | |
---|---|---|
Ease of maintenance / change | No redundancy and hence more easy to maintain and change | Has redundant data and hence less easy to maintain/change |
Ease of Use | More complex queries and hence less easy to understand | Less complex queries and easy to understand |
Query Performance | More foreign keys-and hence more query execution time | Less no. of foreign keys and hence lesser query execution time |
Type of Datawarehouse | Good to use for datawarehouse core to simplify complex relationships (many:many) | Good for datamarts with simple relationships (1:1 or 1:many) |
Joins | Higher number of Joins | Fewer Joins |
Dimension table | It may have more than one dimension table for each dimension | Contains only single dimension table for each dimension |
When to use | When dimension table is relatively big in size, snowflaking is better as it reduces space. | When dimension table contains less number of rows, we can go for Star schema. |
Normalization/ De-Normalization | Dimension Tables are in Normalized form but Fact Table is still in De-Normalized form | Both Dimension and Fact Tables are in De-Normalized form |
Data model | Bottom up approach | Top down approach |
The main difference between star schema and snowflake schema is that
- The star schema is highly denormalized and the snowflake schema is normalized. .
- Performance wise, star schema is good but if we think about memory then snow flake schema is better than star schema.
- A dimension table will not have parent table in star schema, whereas
snow flake schemas have one or more parent tables. - Snow Flake Schema has bottom-up appraoch where as Star has Top-down.
- Star Schema has fewer joins and Snow flake has higher


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Can anybody explain why Single Table is bad for RAM Consumption and Script Run Time?

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OBT (= one big table) / single fact table including all dimensions should be part of this comparison (https://medium.com/dbsql-sme-engineering/one-big-table-vs-dimensional-modeling-on-databricks-sql-755...)
