POSTGRESQL Foreign Key Referencing Primary Keys of two Different Tables

Question

I have two tables Books and Audiobooks, both of which have ISBN as their primary keys. I have a table writtenby that has an isbn attribute that has a foreign key constraint

Answer 1

You could use table inheritance to kinda get the best of both worlds. Create the audiobook_writtenby and books_writtenby with an INHERITS clause referencing the writtenby table. The foreign keys could be defined at the child level as you describe, but you could still reference data at the higher level. (You could also do this with a view, but it sounds like inheritance might be cleaner in this case.)

See the docs:

http://www.postgresql.org/docs/current/interactive/sql-createtable.html

http://www.postgresql.org/docs/current/interactive/tutorial-inheritance.html

http://www.postgresql.org/docs/current/interactive/ddl-inherit.html

Note that you will probably want to add a BEFORE INSERT trigger on the writtenby table if you do this.