Data Warehousing Basics Question: Download Questions PDF
Explain Difference between Snow flake and Star Schema. What are situations where Snow flake Schema is better than Star Schema to use and when the opposite is true?
Answer:
Star schema contains the dimesion tables mapped around one or more fact tables.
It is a denormalised model.
No need to use complicated joins.
Queries results fastly.
Snowflake schema
It is the normalised form of Star schema.
contains indepth joins ,bcas the tbales r splitted in to many pieces.We can easily do modification directly in the tables.
We hav to use comlicated joins ,since we hav more tables .
There will be some delay in processing the Query .
in star schema look like a centerally locate fact table and surrounded by dimention tables . its look like a star thats why people colled as a starschema
in star schema dimention tables are de_normalised but fact table is normalised table
in snow flake schema dimention tables are splitted one or more tables
dimention tables are quit bit a table bit space
here dimention tables are normalised
here having the more no of joins
so the performance degrades
as per the client requirement we used star or snow flake schema
client may ask like data normalised or de_normalised
It is a denormalised model.
No need to use complicated joins.
Queries results fastly.
Snowflake schema
It is the normalised form of Star schema.
contains indepth joins ,bcas the tbales r splitted in to many pieces.We can easily do modification directly in the tables.
We hav to use comlicated joins ,since we hav more tables .
There will be some delay in processing the Query .
in star schema look like a centerally locate fact table and surrounded by dimention tables . its look like a star thats why people colled as a starschema
in star schema dimention tables are de_normalised but fact table is normalised table
in snow flake schema dimention tables are splitted one or more tables
dimention tables are quit bit a table bit space
here dimention tables are normalised
here having the more no of joins
so the performance degrades
as per the client requirement we used star or snow flake schema
client may ask like data normalised or de_normalised
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