Big Data and AI

 Retrieving data is the heart of SQL. In Part II of our beginner-friendly tutorial series, we’ll dive into the four essential techniques that let you extract, filter, summarize, and refine datasets: Basic SELECT Queries Advanced Filtering and Expressions Aggregation and Grouping Subqueries and Derived Tables Mastering these topics will empower you to answer real-world questions, from listing customer orders to calculating monthly sales trends. Basic SELECT Queries The SELECT statement is your gateway to any relational database. You’ll learn how to: Specify columns and use aliases ( SELECT first_name AS fname ) Retrieve all fields with SELECT * for quick previews Limit result sets ( LIMIT 10 , TOP 5 ) to speed up testing Sort data with ORDER BY (ascending/descending) Example: sql SELECT id, first_name, last_name FROM customers ORDER BY last_name ASC; This simple query fetches a clean, ordered list of customer names in seconds. Advanced Filtering and Expressions Once you can pull r...