# SQL Aggregate Functions

Summary: in this tutorial, we will introduce you aggregate function concepts and common SQL aggregate functions.

## Introduction to SQL aggregate functions

An aggregate function allows you to perform a calculation on a set of values to return a single scalar value. We often use aggregate functions with the GROUP BY and HAVING clauses of the SELECT statement.

The following are the most commonly used SQL aggregate functions:

• AVG – calculates the average of a set of values.
• COUNT – counts rows in a specified table or view.
• MIN – gets the minimum value in a set of values.
• MAX – gets the maximum value in a set of values.
• SUM – calculates the sum of values.

Notice that all aggregate functions above ignore `NULL` values except for the `COUNT` function.

## SQL aggregate functions syntax

To call an aggregate function, you use the following syntax:

Let’s examine the syntax above in greater detail:

• First, specify an aggregate function that you want to use e.g., `MIN`, `MAX`, `AVG`, `SUM` or `COUNT`.
• Second, put `DISTINCT` or `ALL` modifier followed by an expression inside parentheses. If you explicitly use `DISTINCT` modifier, the aggregate function ignores duplicate values and only consider the unique values. If you use the `ALL` modifier, the aggregate function uses all values for calculation or evaluation. The  `ALL` modifier is used by default if you do not specify any modifier explicitly.

## SQL aggregate function examples

Let’s take a look some examples of using SQL aggregate functions.

### COUNT function example

To get the number of the products in the `products` table, you use the `COUNT` function as follows:

### AVG function example

To calculate the average units in stock of the products, you use the `AVG` function as follows:

To calculate units in stock by product category, you use the `AVG` function with the  `GROUP BY` clause as follows:

### SUM function example

To calculate the sum of units in stock by product category, you use the `SUM` function with the  `GROUP BY` clause as the following query:

Check it out the SUM function tutorial for more information on how to use the `SUM` function.

### MIN function example

To get the minimum units in stock of products in the products table, you use the MIN function as follows:

To get the maximum units in stock of products in the products table, you use the `MAX` function as shown in the following query:
In this tutorial, we have introduced you to the SQL aggregate functions including the most commonly used functions: `AVG`, `COUNT`, `MIN`, `MAX`, and `SUM`.