SQL Aggregate Functions

An aggregate function is a function that performs a calculation on a set of values, and returns a single value.

Aggregate functions are often used with the GROUP BY clause of the SELECT statement. The GROUP BY clause splits the result-set into groups of values and the aggregate function can be used to return a single value for each group.

The most commonly used SQL aggregate functions are :

MIN() – returns the smallest value within the selected column
MAX() – returns the largest value within the selected column
COUNT() – returns the number of rows in a set
SUM() – returns the total sum of a numerical column
AVG() – returns the average value of a numerical column

Aggregate functions ignore null values (except for COUNT()).

We will go through the aggregate functions above in the next chapters.