SQL is a practical language for gathering, combining, and structuring data stored in relational databases. A sequence of queries and temporary tables can produce a final table for download or direct use by a machine-learning algorithm. section 2.3.1
SELECT df1.product_id, df1.product_name, df1.price, df2.product_description, df2.category, df3.manufacturer, df3.weight FROM df1 JOIN df2 ON df1.product_id = df2.product_id JOIN df3 ON df1.product_id = df3.product_id;
This product-data query demonstrates joining three tables through a shared product identifier and selecting the fields needed for analysis. section 2.3.1
Use SQL when:
- All relevant data resides in a relational database. section 2.3.1
- Multiple event, item, or dimension tables must be consolidated into a coherent dataset. section 2.3.1
- A repeatable series of queries should create an analysis-ready table. section 2.3.1
