Re: Is it Possible to Enforce This Relationship at the DB Level?

On Oct 18, 8:57 pm, Ed Prochak <edproc...@xxxxxxxxx> wrote:
On Oct 16, 7:03 am, David Portas



<REMOVE_BEFORE_REPLYING_dpor...@xxxxxxx> wrote:
On 15 Oct, 22:59, dutone <dut...@xxxxxxxxxxx> wrote:

I'd like to enforce this based on the data model and its
relationships.
Although to me, it doesn't seem possible without an additional layer
of logic.
The need for a check assertion in a RDMS tells me that cerain
cituations must be enforced at a higher level. This is one of them I
guess.

Maybe your definition of a data model differs from mine. All such
constraints are surely part of that model irrespective of what syntax
the DBMS uses.

If you have some particular DBMS in mind then maybe someone will have
other suggestions about features supported by that product. Perhaps a
redesign would also be possible but I'm reluctant to begin a design-by-
newsgroup exercise.

--
David Portas

I'm not trying to start a group design effort, but his original model
certainly seems to me to have the Cell Config in the wrong place. At
the logical lege, the connections should be described verbally (the
cardinality can be there but blank connections between entities leaves
too many unidentified assumptions.

Wrong place, how so? The diagram got screwed up so let me clarify.

The CLIENT can provides a SERVICE

Each SERVICE is described by a SPREAD***

The SPREAD*** must conform to a SPEC

A SPEC mandates that one supply values for its FIELDS

A SPREAD*** has many CELLS which correspond to to FIELDS of its
chose SPEC






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