You've done an **excellent job** and helped the construction company. They have started working on expanding the **Yellow** metro line.


They have **recommended you**, and the **school** has shown interest in you because they also have **several tasks for you**. But first, let's familiarize ourselves with the `student_grades` table they provide:

The table contains grades for exams in various subjects.

The school has a total of **100 students**, information about whom is provided in the given table. There is information in the `class_letter` column, which has 3 options: `A`, `B`, or `C`. The subject name(`subject_name`), as well as the student's grade(`grade`), are included. 

Let's see how many students there are in each class with the following query:



SELECT class_letter, COUNT(DISTINCT student_surname) AS anumber_of_students
FROM student_grades
GROUP BY class_letter

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.

Challenge: Average Student's Grade

Brief Instructions

解答