Re: ER diagram question

In message <28a69e7c.0401200242.1faa3dac_at_posting.google.com>, Jonck van der Kogel <jonck_at_vanderkogel.net> writes
>> Can a Customer have a Communication independent of a Project?
>
>Uuhhhmmm.... good question :-) My original plans were that a Customer
>could only have a Communication coupled to a Project, but now that you
>ask, I think that it would be much better style if a Customer could
>have a Communication independent of a Project.
>But this makes it even more difficult! Do you see a solution?
>Your help is truly much appreciated, Jonck

You imply a 1:M relationship between communications and projects, but although this may make things neater it's not a real-world situation.

Customers are likely to have issues that apply to all, some or just one project. Unless you can constrain them in some way you will just have to live with it. You could create a web form that allows customers to enter one-and-only-one project name in the box, but that is likely to annoy them.

I'm afraid you will just have to live with M:N relationships. Create an entity called Reference which links Communications and Projects. Check each communication and look for references to projects.

-- 
Bernard Peek
London, UK. DBA, Manager, Trainer & Author. Will work for money.