Обсуждение: 3 foreign keys in 1 table for 3 1-to-many relations?

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3 foreign keys in 1 table for 3 1-to-many relations?

От
gvim
Дата:
I have 3 tables A, B & C each of which has a 1-to-many relation with a 
Comments table but I can't fathom how to set up the foreign key(s) in 
Comments without resorting to distinct A_id, B_id & C_id columns in 
Comments and enforcing 2 of the 3 columns be NULL for a given row. Seems 
ugly.

gvim

Re: 3 foreign keys in 1 table for 3 1-to-many relations?

От
"David G. Johnston"
Дата:
On Wed, Jun 17, 2015 at 8:51 PM, gvim <gvimrc@gmail.com> wrote:
I have 3 tables A, B & C each of which has a 1-to-many relation with a Comments table but I can't fathom how to set up the foreign key(s) in Comments without resorting to distinct A_id, B_id & C_id columns in Comments and enforcing 2 of the 3 columns be NULL for a given row. Seems ugly.

You should probably take a look at inheritance and see if it can accommodate your use case.

http://www.postgresql.org/docs/9.4/static/tutorial-inheritance.html

David J​