Summary  
This chapter covers using GROUP BY together with the HAVING clause to filter grouped results based on aggregate conditions.  

General domain of usage  
Academic record management

The school recently held a **competition** for students who participated in **Mathematics**. Some students were rewarded, but now the school wants to ensure no students **cheated** by taking **more than one** exam, including the math exam.

Your task is to **find the last names** of students who took **more than one** exam, with one of them being `Mathematics`.

Here is the query from our **previous assignment** that you can use as an example:



SELECT student_surname, AVG(grade) as average_grade
FROM student_grades
GROUP BY student_surname
HAVING COUNT(grade) > 1

This course is perfect for those who already have a basic understanding of SQL and want to delve into more advanced concepts to craft more powerful queries. Throughout the course, you will become familiar with data grouping and filtering grouped data. You will also learn how to work with multiple tables simultaneously, including how to combine them. Additionally, you will explore different types of table joins and how to apply them in practice.

More Complex Filtering

Brief Instructions

解答