SQL Joins, CTEs and Subqueries Explained Using Hospital Visit Data

The article explains how analysts combine data from related tables in a relational database using SQL joins, window functions and Common Table Expressions. It uses a hospital database with patients, doctors, departments and visits to illustrate these techniques. The visits table links patient activity to clinical and billing details, enabling questions about billing, revenue and comparisons across visits. An example query joins visits with patients and doctors, showing that a patient can appear multiple times because each row represents a separate visit. The author also notes how different join types change query results.