This document discusses how SQL can be used in Lucidworks Fusion for various purposes like aggregating signals to compute relevance scores, ingesting and transforming data from various sources using Spark SQL, enabling self-service analytics through tools like Tableau and PowerBI, and running experiments to compare variants. It provides examples of using SQL for tasks like sessionization with window functions, joining multiple data sources, hiding complex logic in user-defined functions, and powering recommendations. The document recommends SQL in Fusion for tasks like analytics, data ingestion, machine learning, and experimentation.