4.md

Dangers of Duplication

Duplicate data can be hard to keep consistent throughout the database.

Instead of embedding the vendor information, we can create a vendors collection and

reference the vendor document in each potion document.

Potion { "_id": ObjectId(...), "name": "Invisibility", "vendor_id": "Kettlecooked }

Vendor { "_id": "Kettlecooked", "phone": 5555555555, "organic": true }

Inserting Referenced Documents

db.vendors.insert({ "_id": "Kettlecooked", "phone": 5555555555, "organic": true })

db.potions.insert({ "name": "Invisibility", "vendor_id": "Kettlecooked" })

"vendor_id": "Kettlecooked" is the referenced document

Data Modeling Decisions