Hi folks.

I've got a relatively simple task I'd like to perform but not too sure on the 'correct' way pf creating the database schema.

I'll describe my query in the form of an example.

I have table A that contains a list of Servers

Table B contains a list of Services that could be installed on a server

A simple one to many relationship would be created between the two so that any one server could be hosting one or more services.

Now the part I'm stuck on...

I want to create a third entity that will list services that are dependant on each other. E.g. Active Directory is dependant on DNS. Therefore I'd like an entity that would reference two servers - I'm informed you can only have one foriegn key between two tables.

E.g. I can't have field ServerA relating to Services as well as field ServerB also relating to services.

Is this correct? Is there a better way of designing the database?

Hope this makes sense and thanks in advance.
Ryan

Before answering your question, are you sure about that? Can a server not host many services? And can a service not be hosted on many servers?

pootle flump ur codings are working excelent.

sorry, I'll try explain myself a little better. I should have said they'd be four entities. It's been a long day...

-Servers-
ServerID (PK)
HostName
IP

-Services-
ServiceName (PK)
Port

-Paring-
ServerID (FK)
Service (FK)

So the paring table will match what server hosts what service(s). I now need a forth table that will list service dependencies. Something along the lines of:

-Dependencies-
ServerA (FK)
ServerB (FK)

Will an entity allow me to have to FK fields going to the same field in another entity? Is there a better way of acheiving this?

Note: There'll probably be more fields per entity, this is just a basic example.


Thanks

I think you've mentioned it yourself, that "services [...]are dependant on each other", not servers. From that point of view your -Dependencies- entity does not make much sense.

You have a point n_i...

But surely dependant services will still need a way of recording that, and one service can (and are) dependant on greater than one other service.

Yes, why not?