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
ineyman_at_perceptron.com

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> 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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> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Magaliff, Bill
> INET: Bill.Magaliff_at_lendware.com
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Igor Neyman
  INET: ineyman_at_perceptron.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
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