2. Example of Dimensional Data Model
October 14, 2023 2
Star Schema
Snowflake Schema
Fact constellations or Galaxy Schema
Multidimensional Model (Cubes)
3. Snowflakes Schema
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The snowflake schema is a variant of the star
schema. Here, the centralized fact table is
connected to multiple dimensions.
In the snowflake schema, dimensions are
present in a normalized form in multiple related
tables.
The snowflake structures have several levels of
relationship, and the child tables have multiple
parent tables.
5. Snowflakes Schema(Cont.)
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The main idea behind the snowflake schema is that
dimension tables are completely normalized.
Each dimension table can be described by one or more
lookup tables.
Each lookup table can be described by one or more
additional lookup tables.
This is repeated until the model is fully normalized. The
process of normalizing star schema dimension tables is
called snowflaking."
6. Pros and cons of Snowflake
October 14, 2023 DW01: Introduction 6
Benefits of Snowflake Schema:
Data redundancy gets removed upon the creation of new dimension
tables thanks to the hierarchal structure.
Snowflake Schema tends to use less storage space than Star Schema.
Disadvantages of Snowflake Schema:
Due to normalized dimension tables, the ETL system must load the
number of tables.
You may often need to use complex joins while performing queries
due to the large number of tables that has been added.
7. Querying on Star schema and
Snowflake
October 14, 2023 DW01: Introduction 7
8. October 14, 2023 DW01: Introduction 8
How many books were sold in Maharashtra in January 2022 ?
Star Schema
Querying on Star schema and Snowflake
9. October 14, 2023 DW01: Introduction 9
How many books were sold in Maharashtra in January 2022 ?
Snowflake
Querying on Star schema and Snowflake