The school is **pleased with your work** and agrees to **continue the collaboration**. 

Now they have a new task for you. The **top 10 students with the highest average grades** will be offered a trip to a scientific center as a reward. One mandatory condition is receiving a **grade above 90 on the math exam**. To find such students, they have turned to you. 

Let's see what you need to do using our `employee` table as an example.

Suppose you need to find out in **which departments** there are employees who **were hired before 2019** and the **average salary** in those departments. To implement such a task, you can use the following query:








SELECT department, AVG(salary) AS average_salary
FROM employees
WHERE hire_date < '2019-01-01'
GROUP BY department

As you can see, there are only 3 such employees, and we used the necessary tools to achieve this result. 




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.

In this section, you will learn how to group and manage data effectively. We will introduce the GROUP BY operator for grouping data. Additionally, you will learn how to filter grouped data using the HAVING operator.

You will learn about nested subqueries, how to create them, and how to use them effectively.

Here, you will learn how to combine multiple tables, allowing you to work with a unified table and simplify query creation.

Learn the fundamentals of Data Definition Language (DDL) and Data Manipulation Language (DML) in SQL, including how to create, modify, and delete database objects, as well as how to insert, update, and delete data within tables.

Challenge: Searching for the Top Math Students

Solution