Why can you not have a foreign key in a polymorphic association?

Why can you not have a foreign key in a polymorphic association?

ruby-on-rails database foreign-key-relationship polymorphic-associations

database

Any example of a necessary nullable foreign key?

database foreign-key-relationship

database

Can't add AUTO_INCREMENT on existing column because of foreign key

mysql sql database foreign-keys foreign-key-relationship

database

Does making relationships in Database make them slow

database performance foreign-key-relationship

database

Create table fails with Foreign Key Constraint is incorrectly Formed

mysql database foreign-key-relationship mariadb

database

How to Implement Referential Integrity in Subtypes

sql database relational-database foreign-key-relationship

database

Wordpress: difference between site_id and blog_id?

database wordpress foreign-key-relationship

database

MySQL 5.5 foreign key constraint fails when foreign key exists

mysql database foreign-keys foreign-key-relationship mysql5

database

Table composed purely of foreign keys?

sql database database-design foreign-keys foreign-key-relationship

database

Database Design - Column In One Table References Two Tables

database database-design foreign-key-relationship

database

Laravel 5.1 eloquent relations model- how to update foreign key column?

mysql database eloquent laravel-5.1 foreign-key-relationship

database

Can I use the same foreign key constraint in two different tables?

mysql database foreign-keys foreign-key-relationship

database

MySQL - ON update CASCADE + foreign_key_checks = 0

mysql database foreign-keys sql-update foreign-key-relationship

database