Mongodb create collection if not exists nodejs

You can use the following syntax to insert a document into a collection in MongoDB only if it doesn’t already exist:

Table of Contents Show

Example: Insert if Not Exists in MongoDB
Additional Resources
Creating a Collection
Creating a Database
Does MongoDB automatically create Collection if not exists?
How do you check if collection is already exists in MongoDB?
How do I create a node collection in MongoDB?
How do I create a collection in MongoDB without any document using mongoose in node JS?

db.teams.update(
	{
	  team : 'Hornets'
	}, 
	 {
	  $setOnInsert: {team: 'Hornets', points: '58', rebounds: '20'}
	 },
	 {upsert: true}
)

This particular code checks if the field “team” has a value of “Hornets.” If this value exists, then nothing will happen.

However, if this value does not exist then it will insert a document with specific values for the “team”, “points”, and “rebounds” fields.

The following example shows how to use this syntax in practice.

Example: Insert if Not Exists in MongoDB

Suppose we have a collection called teams with the following documents:

db.teams.insertOne({team: "Mavs", points: 30, rebounds: 8})
db.teams.insertOne({team: "Spurs", points: 35, rebounds: 12})
db.teams.insertOne({team: "Rockets", points: 20, rebounds: 7})
db.teams.insertOne({team: "Warriors", points: 25, rebounds: 5})
db.teams.insertOne({team: "Cavs", points: 23, rebounds: 9})

Suppose we use the following code to attempt to insert a document for the team “Mavs”:

db.teams.update(
	{
	  team : 'Mavs'
	}, 
	 {
	  $setOnInsert: {team: 'Mavs', points: '58', rebounds: '20'}
	 },
	 {upsert: true}
)

Since the field “team” already contains information for the “Mavs”, none of the documents will be modified.

However, suppose we use the following code to insert a document for the team “Hornets”:

db.teams.update(
	{
	  team : 'Hornets'
	}, 
	 {
	  $setOnInsert: {team: 'Hornets', points: '58', rebounds: '20'}
	 },
	 {upsert: true}
)

Since the field “team” does not already contain information for the “Hornets”, a new document will be added to the collection with the values that we specified for each field.

Here’s what the updated collection looks like:

{ _id: ObjectId("6203df361e95a9885e1e764a"),
  team: 'Mavs',
  points: 30,
  rebounds: 8 }
{ _id: ObjectId("6203df361e95a9885e1e764b"),
  team: 'Spurs',
  points: 35,
  rebounds: 12 }
{ _id: ObjectId("6203df361e95a9885e1e764c"),
  team: 'Rockets',
  points: 20,
  rebounds: 7 }
{ _id: ObjectId("6203df361e95a9885e1e764d"),
  team: 'Warriors',
  points: 25,
  rebounds: 5 }
{ _id: ObjectId("6203df361e95a9885e1e764e"),
  team: 'Cavs',
  points: 23,
  rebounds: 9 }
{ _id: ObjectId("6203e17de42bfba74fc73325"),
  team: 'Hornets',
  points: '58',
  rebounds: '20' }

Notice that a new document has been added for the “Hornets” team.

Note: You can find the complete documentation for the $upsert function here.

Additional Resources

The following tutorials explain how to perform other common operations in MongoDB:

MongoDB: How to Add a New Field
MongoDB: How to Remove a Field
MongoDB: How to Count Distinct Values in Field

A collection in MongoDB is the same as a table in MySQL

Creating a Collection

To create a collection in MongoDB, use the createCollection() method:

Example

Create a collection called "customers":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.createCollection("customers", function(err, res) {
    if (err) throw err;
    console.log("Collection created!");
    db.close();
});
});

Run example »

Save the code above in a file called "demo_mongodb_createcollection.js" and run the file:

Run "demo_mongodb_createcollection.js"

C:\Users\Your Name>node demo_mongodb_createcollection.js

Which will give you this result:

Important: In MongoDB, a collection is not created until it gets content!

MongoDB waits until you have inserted a document before it actually creates the collection.

Creating a Database

To create a database in MongoDB, start by creating a MongoClient object, then specify a connection URL with the correct ip address and the name of the database you want to create.

MongoDB will create the database if it does not exist, and make a connection to it.

Example

Create a database called "mydb":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/mydb";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
console.log("Database created!");
db.close();
});

Run example »

Save the code above in a file called "demo_create_mongo_db.js" and run the file:

Run "demo_create_mongo_db.js"

C:\Users\Your Name>node demo_create_mongo_db.js

Which will give you this result:

Important: In MongoDB, a database is not created until it gets content!

MongoDB waits until you have created a collection (table), with at least one document (record) before it actually creates the database (and collection).

Does MongoDB automatically create Collection if not exists?

Create a Collection If a collection does not exist, MongoDB creates the collection when you first store data for that collection.

How do you check if collection is already exists in MongoDB?

The collectionExists method can be used to check whether a collection is present or not: MongoClient mongoClient = new MongoClient("localhost", 27017); DB db = mongoClient. getDB("baeldung"); String testCollectionName = "student"; System. out.