Re: Horizontal Mapping Question
Re: Horizontal Mapping Question
- Subject: Re: Horizontal Mapping Question
- From: Ray Ackland <email@hidden>
- Date: Mon, 23 Feb 2004 10:51:23 +1300
Paul,
As I understand it. the primary keys (I assume that's the "id" you
refer to) are shared between the three tables - that is the person
table propagates the pk's to the other tables.
As a result, every entry in the Employee or Customer table also has an
entry (with the same pk) in the person table. Hence there should be no
problem with someone being both an employee and a customer as the pk
will exist in all 3 tables.
If you are using horizontal mapping, then there may be problems as you
use a field with a code indicating what kind of entity they are. This
will be more difficult to get around if you want them to be associated
with two different codes.
Ray.
On 23/02/2004, at 2:39, Paul Mathews wrote:
Hi all
hopefully a quick question about horizontal mapping...The
documentation provides the following
example...
Person
v
v v
Employee Customer
It would seem that the "id's" of the Employee and Customer tables are
unique for both tables, so I
was wondering how the situation of a person being both an Employee and
a Customer is handled?
Are two entries created, one in each table with the same id or am I
completely on the wrong track
and that would be a case for Vertical or Single Table Mapping?
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