Description

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You’re doing research about academic achievement, and you’re studying one particular group of students at a local university. Find the average grade of the five most successful students in this group.

The information about the students’ grades is stored in a table called students, which has the following attributes:

• student_id: the unique identifier of the student;
• student_name: the name of the student;
• grade: the grade that the student achieved.

The result should be a table with one column average_grade and one row that contains the average grade of the five students with the highest grades. The answer should be formatted to 2 digits after the decimal point. It is guaranteed that the five most successful students can be uniquely identified.

Example

For the following tables students

student_id	student_name	grade
1	Oliver Smith	3.2
2	Jacob Bell	2.9
3	William Thompson	3.1
4	Sophie Clark	3.5
5	Daniel Palmer	3.6
6	Emily Morris	4.0
7	Zachary Mills	2.5

the output should be

average_grade
3.48

The top 5 grades for this group are 4.0, 3.6, 3.5, 3.2, and 3.1, so their sum is equal to 17.4 and 17.4 / 5 = 3.48.

• [execution time limit] 10 seconds (mysql)

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/*Please add ; after each select statement*/
CREATE PROCEDURE top5AverageGrade()
BEGIN
	SELECT ROUND(AVG(grade),2) AS average_grade
    FROM (
        SELECT grade
        FROM students
        ORDER BY grade DESC
        LIMIT 5) t;
END