SQL: MIN Function
The MIN function returns the minimum value of an expression.
The syntax for the MIN function is:
SELECT MIN(expression )
For example, you might wish to know the minimum salary of all employees.
SELECT MIN(salary) as "Lowest salary"
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"
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.