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hi friends,
what is star schema and snowflake schema. what are the differences?
1.When you have one Fact Table and Multiple Dimension Tables is a Star schema.
2.When You have a Fact Table it is connected to dimension table and then sub dimension table is a snow flake schema.
One link of many
diffen.com/difference/Snowflake_Schema_vs_Star_Schema
In your data model try use star schema as often as possible.
Snowflake schema is an extension of the star schema, where each point of the star explodes into more points.
It will be harder to read and understand your model
The following diagram shows .....
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Description | Star Schema | Snow Flake 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 |
Regards
Harsha Nandan
STAR schema::one central fact table connected to multiple dimension tables is star.
SNOWFLAKE::it is extension of star,one fact table connected to multiple dimensions with sub dimesion tables this is called snowflake ...if possible try for make snowflake to star because star is very user friendly more understanding manner and star contain less joins so performance is good than snowflake.
Hi,
Start schema is where a fact table is directly linked with multiple denormalised dimension tables.
Snowflake scheema is where a fact table is dirctly or indirectly linked with normalised dimension tables. (dimension tables are linked with other dimension tables)
Thanbks and Regards,
Ankita