Up down or Down up. Understanding Subqueries and CTEs in SQL: A Comprehensive Guide

Introduction When working with databases, there comes a time when a simple SELECT statement is not enough to answer complex questions. Imagine you need to find customers who spent more than the average spent by all customers, or products that have never been sold, or employees who earn more than their department's average salary. These are the moments when subqueries and Common Table Expressions (CTEs) become essential tools in your SQL toolkit. This article explores subqueries and CTEs in depth