jared:
any thoughts on the point at which this becomes a potential performance
bottleneck? pretty simple if there are two potential fk's as in your
example - but what about 4 or 5 fk id's?
-biill
-----Original Message-----
Sent: Thursday, August 01, 2002 1:48 PM
To: Multiple recipients of list ORACLE-L
> btw, in your first solution, how are you going to implement mutual
> exclusiveness of EMPLOYEE_ID and SUPLIER_ID? trigger? - not very
elegant.
Actually quite simple and elegant:
alter table add constraint only_one
( check (
( employee_id is null and supplier_id is not null )
or
( supplier_id is null and employee_id is not null )
)
)
Jared
"Igor Neyman" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
07/31/2002 02:20 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
cc:
Subject: Re: data modeling question - child table with
multiple parents
yet, another solution:
add another table, called i.e. "ACTOR" (actor_id, actor_type);
sub-entity tables "EMPLOYEE", "SUPLLIER", "CONTRACTOR" will store
sub-entity
specific information, and their PK (employee_id, supplier_id, ...) will be
foreign keys to actor_id in "ACTOR" table;
table "ADDRESS" will reference "ACTOR" table (not multiple sub-entities),
and you can enforce this relationship in the database;
thus, adding new sub_entity (like "VENDOR") will not require any changes
in
existing tables;
also, you can implement "TELEPHONE" table the same way (referencing
"ACTOR"
table).
btw, in your first solution, how are you going to implement mutual
exclusiveness of EMPLOYEE_ID and SUPLIER_ID? trigger? - not very elegant.
Igor Neyman, OCP DBA
[EMAIL PROTECTED]
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Wednesday, July 31, 2002 4:43 PM
> Good day, all:
>
> Am curious to hear opinions on how to model a child table that has
multiple
> parent tables (i.e., foreign key to multiple parents)
>
> Example:
> There's a table that stores Addresses (table ADDRESS) for both employees
> (table EMPLOYEE) and suppliers (table SUPPLIER).
>
> Each of these tables has a Primary Key field called ID.
>
> One way to set this up would be for the ADDRESS table to have 2 fields,
> EMPLOYEE_ID and SUPPLIER_ID, which would be mutually exclusive (i.e.,
one
or
> the other, to indicate the parent record of the address).
>
> Another solutions if for the ADDRESS table to have two fields to
indicate
> the parent table name and parent table pk value.
>
> The first method enables me (the dba) to create foreign keys from the
> address table to each of the parent tables to validate data. The second
> method does not enable me to create such foreign keys (leaving it to the
> developers to validate date and insure referential integrity) but would
also
> easily facilitate the addition of other parent tables (e.g., CONTRACTOR,
> VENDOR, etc.) without altering the ADDRESS table itself.
>
> Any and all thoughts, comments, opinions, experiences are most welcome.
>
> Thanks!
> bill magaliff
>
>
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> Author: Magaliff, Bill
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