Construct calculations within a database using SQL’s aggregate functions

• Aggregate functions allow calculations to be performed on data in a database.

AVG

SELECT AVG(attribute) FROM table_name;

SELECT AVG(age) FROM student;

SELECT AVG(score)
FROM student
WHERE score > 87;

COUNT

SELECT COUNT(attribute) FROM table_name;

SELECT COUNT(StudentID) FROM Students;

SUM

SELECT SUM(attribute) FROM table_name;

SELECT SUM(score) FROM Students;

MIN and MAX

SELECT MIN(attribute) FROM table_name;
SELECT MAX(attribute) FROM table_name;

SELECT MIN(score) FROM Students;
SELECT MAX(score) FROM Students;

Aggregate functions with GROUP BY

SELECT subject, AVG(score) AS average_score
FROM Subjects
GROUP BY subject;

SELECT CustomerCountry, COUNT(CustomerID)
FROM Customer
GROUP BY CustomerCountry;

Aggregate functions with HAVING

SELECT CustomerCountry, COUNT(CustomerID)
FROM Customer
GROUP BY CustomerCountry
HAVING COUNT(CustomerID) > 2;