Lesson #8: Transformations
This lesson focuses two things. First, how to selectively aggregate numeric values in the database. Second, on how to merge offsetting financial data from an external data source into the database in bulk.
Selective aggregation is the process of using the CASE statement inside an aggregation function, like the some. You can alternatively use another procedure construct like Oracle’s DECODE or MySQL’s IFNULL function over the generic CASE statement.
The loading examples focus on importing Comma Separated Value (CSV) files into tables. These are often critical skills in any Extract, Transform, and Load (ETL) operation of a data warehouse or major data migration effort.
- Advanced Aggregation
- Learn how to use expressions in the
GROUP BYclause. - Basic Transformation
- Learn how to shift aggregated sets of data into columns based on selective aggregation.
- Hierarchical Queries
- Learn how to use hierarchical queries to traverse a tree structure maintained through a recursive relationship.
