# Aggregate Function in SQL

An aggregate function in SQL performs a calculation on a set of values and returns a single value. Common aggregate functions include `COUNT()`, `SUM()`, `AVG()`, `MAX()`, and `MIN()`.

## Examples of Aggregate Functions:

Assume we have the following `employees` table:

1. COUNT(): Returns the number of rows that match a specified condition.

```SELECT COUNT(*) AS total_employees FROM employees;

```
` Result:   total_employees   ----------------   5          `

2. SUM(): Returns the sum of a numeric column.

```SELECT SUM(salary) AS total_salary FROM employees;
```
` Result:   total_salary    --------------    31500        `

3. AVG(): Returns the average value of a numeric column.

```SELECT AVG(salary) AS average_salary FROM employees;

```
`Result:   average_salary    ----------------    6300       `

4. MAX(): Returns the maximum value in a set.

```SELECT MAX(salary) AS highest_salary FROM employees;

```
`Result:  highest_salary   ----------------   8000    `

5. MIN(): Returns the minimum value in a set.

```SELECT MIN(salary) AS lowest_salary FROM employees;

```
` Result:   lowest_salary    ---------------    5000 `