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Why ETL?
ETL is all about optimization
A relational database can be optimized in either of two forms:
- Normalized for transactional processing
- Goal is to prevent “update anomalies”
- “3rd Normal Form”, 3NF
- Denormalized for slice-and-dice reporting
- The Dimensional Model, a/k/a star schema
Source data (like a spreadsheet) may not be normalized at all
ETL is essential for getting our data into the a usable dimensional form