Chapter 1

Chapter 2

Chapter 3 : Creating and manipulating Document

Create document

• we can use the insert()

• When insert the document, the _id is automatically create with unique value of ObjectId. Each document have different _id.

• Cannot insert the same value of _id to the collection.

• _id can be anything as long as unique. But if the document insert does not have _id, mongoDB will assign as ObjectId

• Insert order:

  db.inspections.insert([{ "_id": 1, "test": 1 },{ "_id": 1, "test": 2 }, { "_id": 3, "test": 3 }])

  • Above command have the same _id , the second document (which test = 2) will not add. But when insert is ran, only 1 document is inserted instead of two.
  • This because when many documents are inserted the default configuration is the document is inserted with order. If we want to change, we need to pass { "ordered": false } to the insert()

  db.inspections.insert([{ "_id": 1, "test": 1 },{ "_id": 1, "test": 2 }, { "_id": 3, "test": 3 }],{ "ordered": false })

Update documents

• To update the document, we can use updateOne() and updateMany()
• format for update : db.<collection_name>.updateOne({query},{update_operator})
• example : db.zips.updateOne({ "city": "HUDSON" }, { "$inc": { "pop": 10 }})
  • here we can see, the db will find the document with the city = HUDSON and update the pop value by increment with 10.

• When update the field that does not exist in the document, the field will be created to that document.

Delete document