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 commonly used with the GROUP BY clause of the SELECT statement. The GROUP BY clause divides the result-set into groups of values, and the aggregate function returns a single value for each group.

Common Aggregate Functions

• MIN() – Returns the smallest value in the selected column.
• MAX() – Returns the largest value in the selected column.
• COUNT() – Returns the number of rows in a set.
• SUM() – Returns the total sum of a numeric column.
• AVG() – Returns the average value of a numeric column.

🔹 Note: Aggregate functions ignore NULL values, except for COUNT().

Example

SELECT department, COUNT(*) AS total_employees
FROM employee
GROUP BY department;

SQL MIN() and MAX() Functions

The MIN() and MAX() functions are used to retrieve the smallest and largest values from a specified column.

MIN() Function

• Returns the smallest value of the selected column.

SELECT MIN(column_name)
FROM table_name
WHERE condition;

MAX() Function

• Returns the largest value of the selected column.

Syntax

SELECT MAX(column_name)
FROM table_name
WHERE condition;

The SQL COUNT() Function

The COUNT() function returns the number of rows that match a specified condition.

Syntax

SELECT COUNT(*)
FROM table_name;

The SQL SUM() Function

The SUM() function returns the total sum of a numeric column.

Syntax

SELECT SUM(column_name)
FROM table_name;

The SQL AVG() Function

The AVG() function returns the average value of a numeric column.

Syntax

SELECT AVG(column_name)
FROM table_name;