Understanding Joins and Window Functions in SQL

Two of the most powerful SQL concepts a data person, like a data analyst or a backend developer, will use are "Joins" and "Window Functions." "Joins" are used to combine data from multiple tables, and "Window Functions" are used to perform complex calculations on related rows of data without aggregating the results. In this article, I will explain what "Joins" and "Window Functions" are, along with examples, in a very simple way. Part 1: SQL Join In relational databases, data is often stored in multiple tables. For example, you might have: • customers table • orders table Each table stores different information, but they are connected using a common key like customer_id. What Is a Join? A JOIN combines rows from two or more tables based on a related column. Think of it like matching records from one Excel sheet to another using a common ID Types of Joins 1. INNER JOIN Returns only the matching records in both tables. SELECT c.customer_id, c.name, o.order_id, o.order_date FROM customers