Re: Database normalization

I have a fairly basic question about database design where im not sure which approach is considered correct.

I have two different entities: Clients and Services. Both allow users to add progressive updates about the two entities.

The update/message format is exactly the same for both. Should I make two different tables:

  client_updates and service_updates
  or
  one table with extra columns : is_client, client_id, service_id, where either client_id or service_id would be null depending on the is_client boolean?

The major problem is simply relating the foreign key in the updates table back to the correct entity, client or service.

Regards,
Sebastian