SQL COUNT, AVG, SUM

Definition: These aggregate functions summarise a column: COUNT() counts rows, AVG() averages a number column, and SUM() adds it up.

Example 1 — how many customers?

SELECT COUNT(*) FROM Customers;

COUNT(*) counts every row.

Example 2 — average product price

SELECT AVG(Price) FROM Products;

Example 3 — total quantity ordered

SELECT SUM(Quantity) FROM Orders;

Example 4 — combine with a condition

SELECT COUNT(*) AS GermanCustomers
FROM Customers
WHERE Country = 'Germany';

💡 Tip: aggregate functions become really powerful with GROUP BY, which you will meet at the end of this course.