SQL: MIN Function

The MIN function returns the minimum value of an expression.
The syntax for the MIN function is:
SELECT MIN(expression )
FROM tables
WHERE predicates;

Simple Example

For example, you might wish to know the minimum salary of all employees.
SELECT MIN(salary) as "Lowest salary"
FROM employees;
In this example, we've aliased the min(salary) field as "Lowest salary". As a result, "Lowest salary" will display as the field name when the result set is returned.

Example using GROUP BY

In some cases, you will be required to use a GROUP BY clause with the MIN function.
For example, you could also use the MIN function to return the name of each department and the minimum salary in the department.
SELECT department, MIN(salary) as "Lowest salary"
FROM employees
GROUP BY department;
Because you have listed one column in your SELECT statement that is not encapsulated in the MIN function, you must use a GROUP BY clause. The department field must, therefore, be listed in the GROUP BY section.