Re: Can FK be nullable/optional by design?

"Trey Walpole" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> depends on what a Group is and how it is used...
> 
> e.g.,
> is a Group a Super-Client? -- individual Clients may be subsidiaries of a
> Super-Client?
> is a Group in internal designation, like a Sales territory?
> 
> How many Clients are there likely to be w/o a group?
> When you need to act on the clients that are grouped, do you also need to
> act on the clients that are not grouped?
> 
> [ps. in Case B, where did PersonID come from? Is that the Client?]

Yes, it does.
It should be this way

[ps. in Case B, where did PersonID come from? Is that the Client?]

Case B
Group(GroupID PK, Name, GroupCode.)
Client (ClientID PK, Name, ..)
Subtype:
GroupedClient (ClientID PK/FK, GroupID FK NOT NULL)