retrieve average rating on a join

Good Day 

I need help with result. I have a model that returns all business branches. 
I would like to join an additional table called Ratings and return the average rating for each company.

Does anyone have a simple script i can use. What's the best practice to achieve this.

Thanks in advance

PHP Code:

function getAllBranches()
    {
        $db      = \Config\Database::connect();
        $builder = $db->table('branches');
        $builder->join('companies', 'companies.id = branches.companyId');
        $builder->join('businessprofile', 'businessprofile.companyId = branches.companyId'); 
        
        $builder->where('paymentstatus', 'active');
        
        $query = $builder->get();
        
        return $query->getResult();
    }