What are aggregate functions in SQL?

A function is a unit of code that is used for the reusability of a program. An SQL aggregate function calculates on a set of values and returns a single value. The function should return a value. Some SQL aggregate functions are as follows:

• AVG() - It returns the average of a set.
• COUNT() - It returns the number of items in a set.
• MAX() - It returns the maximum value in a set.
• MIN() - It returns the minimum value in a set.
• SUM() - It returns the sum of all or distinct values in a set.