CRUD Operations

• Create
• Read
• Update
• Delete

Inserting a new document in MongoDB

• Insert a new document using the Atlas User Interface.

  • A popup window is provided where we insert our respective values
  • Every MongoDB document must have a unique field _id value. This value must be unique for each document
  • MongoDB allows two documents to be distinct or exactly the same but with different IDs. This is generally not a good practice of data modelling.

  <aside> 💡 You can take the M320 Data Modelling course for MongoDB.

  </aside>

  

• Insert a document using the mongo shell

  • Connect to your Atlas Cluster in the Shell with the URI
  • use <database name>
  • Before inserting, to refer to the structure of the document we can issue the db.inspections.findOne() command in the shell which will return a random document from that collection
  • You might get a duplication key error E11000 code if the document to be inserted does not have a unique _id
  • If you do not specify an _id field, then MongoDB automatically generates one for you.

  <aside> 💡 MongoDB also has a Schema Validation functionality that allows you to enforce document structure

  </aside>

  db.inspections.insert({
  	"_id" : ObjectId("56d61033a378eccde8a8354f"),
    "id" : "10021-2015-ENFO",
    "certificate_number" : 9278806,
    "business_name" : "ATLIXCO DELI GROCERY INC.",
    "date" : "Feb 20 2015",
    "result" : "No Violation Issued",
    "sector" : "Cigarette Retail Dealer - 127",
    "address" : {
            "city" : "RIDGEWOOD",
            "zip" : 11385,
            "street" : "MENAHAN ST",
            "number" : 1712
       }
  })
  

Multiple Documents can also be inserted at a time, We can do this by passing a list of documents to the insert command

db.inspections.insert([
	{"name" : "value"},
	{"name" : "value"},
	{"name" : "value"},	
])

• Sometimes when multiple documents are to be inserted at a time and if one of the documents faces an error, then all the documents subsequent to it would not be inserted and the operation would stop. To prevent this behavior, we can use the {"ordered": false} in the insert method.

db.inspections.insert([
	{"_id" : "value"},
	{"_id" : "value"},
	{"_id" : "value2"},	
], {"ordered": false})

Update Operations

• Documents can be easily updated from MongoDB Atlas easily using the user interface

• Updating documents using the mongo shell

  • Connect to MongoDB Atlas
  • we can update documents using these two commands: updateOne() and updateMany()
  • The commands take two arguments. first is the find query that will find those documents and another is a document which specifies the change that needs to happen
  • Let's say, we need to increase a field of population (pop) to every city of the New York State.

  db.zips.updateMany(
  	{"state": "NY"},
  	{"
  		$inc": {
  			"pop": 10
  		}
  	}
  )
  

  • If no matching field is found to update, then the specified field is created with that value.
  • Along with $inc operator, there are many others out of which some are stated below:
    • $set - Sets the specified value
    • $push - Adds an element to an array field