Lectures

Learn how to use the GROUP BY operator in SQL to group data, apply aggregate functions, and build structured reports. Examples, syntax, common mistakes, and grouping quirks — everything you need to confidently work with aggregated data.

Learn how to filter aggregated data in SQL using the HAVING operator: how it's different from WHERE, syntax, examples, and common mistakes.

A detailed explanation of the differences between WHERE and HAVING in SQL, the order of operations, practical examples, and common mistakes. Find out when to use WHERE, when to use HAVING, and how to properly filter rows and groups in your queries.

In this lecture, you'll learn how to use the main SQL numeric functions for rounding, getting the remainder, raising to a power, and extracting the square root. We'll check out practical examples and common mistakes when working with numbers in queries.

Let's break down the most common mistakes when using aggregate functions in SQL: from wrong GROUP BY usage to NULL traps and query optimization.