Thanks Tom, I wish I'd said that.
Haven't done enough modeling lately...
Jared
"Magaliff, Bill" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
07/31/2002 02:10 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]>
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Subject: RE: data modeling question - child table with multiple parents
thanks, tom . . .
your second option is one I had suggested below, which in may ways is
preferable - easy to track FK relationships, cascade delte, enforce r/i,
etc.
your first option won't work in our case - the parent tables are too
dissimilar to enable us to combine them - more real life example is
storing
the address of a person and the address of an asset (e.g., property) . . .
both addresses need to contain the same type of info, but they belong to
two
entirely different beasts.
I'm working on separating them out - preferable to have multiple address
tables, I think, that each store a unique type of data - but in the
meantime
we've created a mishmash (how exactly do you spell that?)
gather the option of parent_table/parent_pk doesn't work for you?
thanks
-bill
-----Original Message-----
Sent: Wednesday, July 31, 2002 4:00 PM
To: '[EMAIL PROTECTED]'
Cc: '[EMAIL PROTECTED]'
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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