(Day 67 of 100) PostgreSQL Cheat Sheet
1 min readApr 1, 2019
- on_delete SQL standards
CASCADE: When the referenced object is deleted, also delete the objects that have references to it (When you remove a blog post for instance, you might want to delete comments as well). SQL equivalent:CASCADE.PROTECT: Forbid the deletion of the referenced object. To delete it you will have to delete all objects that reference it manually. SQL equivalent:RESTRICT.SET_NULL: Set the reference to NULL (requires the field to be nullable). For instance, when you delete a User, you might want to keep the comments he posted on blog posts, but say it was posted by an anonymous (or deleted) user. SQL equivalent:SET NULL.SET_DEFAULT: Set the default value. SQL equivalent:SET DEFAULT.SET(...): Set a given value. This one is not part of the SQL standard and is entirely handled by Django.DO_NOTHING: Probably a very bad idea since this would create integrity issues in your database (referencing an object that actually doesn't exist). SQL equivalent:NO ACTION.
