Oracle-L: RE: data modeling question - child table with multiple parents

From: Mercadante, Thomas F <NDATFM_at_labor.state.ny.us>
Date: Wed, 31 Jul 2002 13:04:21 -0800
Message-ID: <F001.004A7FEC.20020731130421@fatcity.com>

Bill,

simply combine the employee, supplier, contractor and vendor tables into one such table titled "people". Add a column to indicate what type of record it is (a code indicating one of the above). solves your problem.

if this is not possible, then the address table could have multiple columns, one for each of the tables above with a FK pointing to the master table. however, none of these columns can be the PK for the address tables - you will need to create a column (supported by a sequence) that will contain the PK. I would also then add a column in the address table indicating what type of record this address is for - employee, supplier, etc.

I would go with the first option if at all possible.

Hope this helps.

Tom Mercadante
Oracle Certified Professional

-----Original Message-----
Sent: Wednesday, July 31, 2002 4:43 PM
To: Multiple recipients of list ORACLE-L

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
INET: Bill.Magaliff_at_lendware.com

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Author: Mercadante, Thomas F
INET: NDATFM_at_labor.state.ny.us

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