Why Joins (Relational Model Recap)
Recap the relational model, normalised tables, foreign keys, and why JOIN is the bridge that reassembles data across tables.
Normalisation in One Picture
Instead of duplicating data, you split it across tables:
users— id, name, emailorders— id, user_id, total
Each order references a user by id, not by storing the user's name and email again.
Why Normalise?
Benefits:
- No duplication — change a user's email in one place
- Smaller tables — better cache hit rate
- Constraints enforce relationships
All lessons in this course
- Why Joins (Relational Model Recap)
- INNER JOIN Mechanics
- LEFT/RIGHT JOIN and OUTER Joins
- Self-Joins and Aliases