how to implement an AND logical operator type of validation in laravel

I want to know how to implement a type of validation whereby an error will only occur if both fields have had the exact input before.

For example: if username: Andy Roddick division: New York is already in the database,

username: Andy Roddick division: Texas is fine,

username: Lebron James division: New York is fine,

but username: Andy Roddick division: New York will throw an error.

This is the code i'm using.

$this->validate($request, [
        'username' =>'required',
        'division' =>'required',
     ]);

via Chebli Mohamed