A Beginner's Guide to SQL Joins and Window Functions

Structured Query Language (SQL) is the backbone of data management, enabling us to interact with and extract meaningful insights from relational databases. Two powerful concepts within SQL that are essential for any data professional are Joins and Window Functions. This article will demystify these concepts, providing clear explanations and practical examples based on a hypothetical e-commerce database. Our database consists of four tables: • Customers: customer_id, first_name, last_name, email, phone_number, registration_date, membership_status • Inventory: product_id, stock_quantity • Products: product_id, product_name, category, price, supplier, stock_quantity • Sales: sale_id, customer_id, product_id, quantity_sold, sale_date, total_amount Understanding SQL Joins: Connecting Related Data In relational databases, data is often spread across multiple tables to ensure efficiency and reduce redundancy. Joins are SQL clauses that combine rows from two or more tables based on a related c