I think you have the relationships reversed. If a company can be one of
many
different types, your relationships should be:
Company
belongs_to :company_type, :foreign_key => ‘ctype_id’
CompanyType
has_many :companies
and your tables should be:
Company
id
…
ctype_id
Company_Types
id
ctype
…
Now you may change the value for ctype in the Company Types table and
the
changes will be reflected in all the companies that reference that
company
type. eg