Coql

I want to use Coql to get all Deals where a specific field is null, and then I want the Contact_Name like "Peter Johnson".

With fields like Modified_By, Contact_Name, Created_By etc, I can access the email and id fields by using dot notation like "Contact_Name.id or Contact_Name.email" which returns me the data I want.

There is however also a "name" property, but when I run Contact_Name.name, I get the error :

{"code":"INVALID_QUERY","details":{"column_name":"Contact_Name.name"},"message":"column given seems to be invalid","status":"error"}

Please assist