Aggregate Functions

In SQL, aggregate functions perform a calculation on a set of values and return a single value. They are often used with the GROUP BY clause of the SELECT statement.

Note: Except for COUNT(*), aggregate functions ignore all NULL values.

Example

List all the years and their number of movies, but only the years with more than 5 movies:

SELECT year,
  COUNT(*)
FROM movies
GROUP BY year
HAVING COUNT(*) > 5;