Foreign Keys, Explained Like You're Five

Описание: This toy belongs to kid number 99. But there is no kid 99.
Bitsy explains foreign keys with toy tags that must point at a real cubby.

More lessons: bitsyexplains.com

What you'll learn:
What a foreign key is
Why SQLite needs PRAGMA foreign_keys = ON
How it blocks bad links, in both directions
The twist: a toy with a NULL owner is allowed

Rule of thumb: When one table points at another, add a foreign key, so every link points at a real row.

Chapters:
0:00 Explain like I'm five
0:27 Foreign keys in code
1:05 Bonus twist: no owner at all, and the rule of thumb

Bitsy Explains: big ideas, explained like you're five. JavaScript, Python, AI, databases, system design, math and medicine.

#sql #database #coding