Database foreign key from multiplier tables

Question

I've facing a trouble, and i need your help please:

If we assume is that there is a table called page has and id, name, and creation_date.

Also if there's another table called user has and id, name, birthdate.

Also if there's another table called admin has and id, name, is_super_admin

The last table is post has writer and content.

The problem is that: the post write can be an page or an user or an admin. So how can i set the post.writer column as foreign key from all of (page.id, user.id and admin.id). How can the database define is that for example [writer = "1"] refers for a an page, admin or an user?

http://stackoverflow.com/questions/3383300/foreign-key-to-one-of-many-tables — Tymur Gubayev, Dec 22 '16 at 18:13

score 0 · Answer 1 · answered Dec 22 '16 at 18:28

Your common elements are id and name between page, user and admin. The "is_super_admin" is a property of an admin level user, and the property "birthdate" belongs to "users", and "creation_date" belongs to pages. One can make the argument that "birthdate" and "creation_date" are synonymous. Assemble your common elements into a single entities table and use additional child tables to hold the unique properties. Define your table schema based on the data, not the real world objects being represented.

Database foreign key from multiplier tables

1 Answers1