Ever written a query… And halfway through forgot what you were doing? You start simple: SELECT * FROM books; Then suddenly you're nesting queries inside queries… Adding conditions inside conditions… And now your SQL looks like a maze you can’t escape. That’s exactly where Subqueries and CTEs (Common Table Expressions) come in. Let’s break them down. What is a subquery? A subquery is just a query inside another query. Think of it like this: “Get me results… based on another result.” It runs first, then feeds its result into the main query. Example: Find books priced above average SELECT title, price FROM books WHERE price > (SELECT AVG(price) FROM books); What’s happening here: The inner query calculates the average price The outer query filters books above that value * When Should You Use Subqueries? * Subqueries are perfect when you want to: Filter data using another query Compare values dynamically Avoid writing multiple separate queries Keep logic compact * Types of Subqueries.…