Answers for "return validation error if value is empty laravel database"

how validate data if is exist must not be empty in laravel

$request->validate([
            'room_id'=>'sometimes|required',
            'doctor_id'=>'sometimes|required',
            'patient_id'=>'sometimes|required',
        ]);

how to set a validation on a value if its not null in laravel php

'password' => 'nullable|min:6|confirmed',