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Nodejs & MongoDB Assignment Help | NodeJs Using MongoDB Tutorial 1



Node.js MongoDB

Node.js can be used in database applications.

One of the most popular NoSQL database is MongoDB.


MongoDB

To be able to experiment with the code examples, you will need access to a MongoDB database.

You can download a free MongoDB database at https://www.mongodb.com.


Or get started right away with a MongoDB cloud service at https://www.mongodb.com/cloud/atlas.


Install MongoDB Driver

Let us try to access a MongoDB database with Node.js.


To download and install the official MongoDB driver, open the Command Terminal and execute the following:


Download and install mongodb package:


C:\Users\Your Name>npm install mongodb 

Now you have downloaded and installed a mongodb database driver.


Node.js can use this module to manipulate MongoDB databases: var mongo = require('mongodb');


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(); 
}); 

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:

Database created!


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).


Creating a Collection

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

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();
 });
});


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:

Collection created!


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.


Insert Into Collection

To insert a record, or document as it is called in MongoDB, into a collection, we use the insertOne() method.


A document in MongoDB is the same as a record in MySQL


The first parameter of the insertOne() method is an object containing the name(s) and value(s) of each field in the document you want to insert.


It also takes a callback function where you can work with any errors, or the result of the insertion:


Example

Insert a document in the "customers" collection:

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");
var myobj = { name: "Company Inc", address: "Highway 37" };
 dbo.collection("customers").insertOne(myobj, function(err, res) {
if (err) throw err;
 console.log("1 document inserted");
 db.close();
 });
});

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

Run "demo_mongodb_insert.js"

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

Which will give you this result:

1 document inserted


Note: If you try to insert documents in a collection that do not exist, MongoDB will create the collection automatically.


Insert Multiple Documents

To insert multiple documents into a collection in MongoDB, we use the insertMany() method.


The first parameter of the insertMany() method is an array of objects, containing the data you want to insert.


It also takes a callback function where you can work with any errors, or the result of the insertion:


Example

Insert multiple documents in the "customers" collection:


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");
var myobj = [
 { name: 'John', address: 'Highway 71'},
{ name: 'Peter', address: 'Lowstreet 4'},
 { name: 'Amy', address: 'Apple st 652'},
 { name: 'Hannah', address: 'Mountain 21'},
 { name: 'Michael', address: 'Valley 345'},
 { name: 'Sandy', address: 'Ocean blvd 2'},
{ name: 'Betty', address: 'Green Grass 1'},
 { name: 'Richard', address: 'Sky st 331'},
 { name: 'Susan', address: 'One way 98'},
 { name: 'Vicky', address: 'Yellow Garden 2'},
 { name: 'Ben', address: 'Park Lane 38'},
 { name: 'William', address: 'Central st 954'},
{ name: 'Chuck', address: 'Main Road 989'},
 { name: 'Viola', address: 'Sideway 1633'}
 ];
 dbo.collection("customers").insertMany(myobj, function(err, res) {
if (err) throw err;
console.log("Number of documents inserted: " + res.insertedCount);
db.close();
 });
});


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

Run "demo_mongodb_insert_multiple.js"

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

Which will give you this result:

Number of documents inserted: 14


The Result Object

When executing the insertMany() method, a result object is returned.

The result object contains information about how the insertion affected the database.

The object returned from the example above looked like this:


{
 result: { ok: 1, n: 14 },
 ops: [
 { name: 'John', address: 'Highway 71', _id: 58fdbf5c0ef8a50b4cdd9a84 },
{ name: 'Peter', address: 'Lowstreet 4', _id: 58fdbf5c0ef8a50b4cdd9a85 },
{ name: 'Amy', address: 'Apple st 652', _id: 58fdbf5c0ef8a50b4cdd9a86 },
{ name: 'Hannah', address: 'Mountain 21', _id: 58fdbf5c0ef8a50b4cdd9a87 },
{ name: 'Michael', address: 'Valley 345', _id: 58fdbf5c0ef8a50b4cdd9a88 },
{ name: 'Sandy', address: 'Ocean blvd 2', _id: 58fdbf5c0ef8a50b4cdd9a89 },
{ name: 'Betty', address: 'Green Grass 1', _id: 58fdbf5c0ef8a50b4cdd9a8a },
{ name: 'Richard', address: 'Sky st 331', _id: 58fdbf5c0ef8a50b4cdd9a8b },
{ name: 'Susan', address: 'One way 98', _id: 58fdbf5c0ef8a50b4cdd9a8c },
{ name: 'Vicky', address: 'Yellow Garden 2', _id: 58fdbf5c0ef8a50b4cdd9a8d },
{ name: 'Ben', address: 'Park Lane 38', _id: 58fdbf5c0ef8a50b4cdd9a8e },
{ name: 'William', address: 'Central st 954', _id: 58fdbf5c0ef8a50b4cdd9a8f },
{ name: 'Chuck', address: 'Main Road 989', _id: 58fdbf5c0ef8a50b4cdd9a90 },
{ name: 'Viola', address: 'Sideway 1633', _id: 58fdbf5c0ef8a50b4cdd9a91 } ],
insertedCount: 14,
 insertedIds: [
58fdbf5c0ef8a50b4cdd9a84,
 58fdbf5c0ef8a50b4cdd9a85,
58fdbf5c0ef8a50b4cdd9a86,
 58fdbf5c0ef8a50b4cdd9a87,
58fdbf5c0ef8a50b4cdd9a88,
 58fdbf5c0ef8a50b4cdd9a89,
58fdbf5c0ef8a50b4cdd9a8a,
 58fdbf5c0ef8a50b4cdd9a8b,
58fdbf5c0ef8a50b4cdd9a8c,
 58fdbf5c0ef8a50b4cdd9a8d,
58fdbf5c0ef8a50b4cdd9a8e,
 58fdbf5c0ef8a50b4cdd9a8f
58fdbf5c0ef8a50b4cdd9a90,
 58fdbf5c0ef8a50b4cdd9a91 ]
}

The values of the properties can be displayed like this:


Example

Return the number of inserted documents:

console.log(res.insertedCount) 

Which will produce this result:

14


The _id Field

If you do not specify an _id field, then MongoDB will add one for you and assign a unique id for each document.


In the example above no _id field was specified, and as you can see from the result object, MongoDB assigned a unique _id for each document.


If you do specify the _id field, the value must be unique for each document:


Example

Insert three records in a "products" table, with specified _id fields:

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");
var myobj = [
 { _id: 154, name: 'Chocolate Heaven'},
 { _id: 155, name: 'Tasty Lemon'},
 { _id: 156, name: 'Vanilla Dream'}
 ];
 dbo.collection("products").insertMany(myobj, function(err, res) {
if (err) throw err;
console.log(res);
 db.close();
 });
});

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

Run "demo_mongodb_insert_id.js"

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

Which will give you this result:

{
 result: { ok: 1, n: 3 },
 ops: [
 { _id: 154, name: 'Chocolate Heaven },
 { _id: 155, name: 'Tasty Lemon },
 { _id: 156, name: 'Vanilla Dream } ],
 insertedCount: 3,
 insertedIds: [
 154,
 155,
 156 ]
}

Find One

In MongoDB we use the find and findOne methods to find data in a collection.


Just like the SELECT statement is used to find data in a table in a MySQL database.


To select data from a collection in MongoDB, we can use the findOne() method.


The findOne() method returns the first occurrence in the selection.


The first parameter of the findOne() method is a query object. In this example we use an empty query object, which selects all documents in a collection (but returns only the first document).


Example

Find the first document in the customers collection:

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.collection("customers").findOne({}, function(err, result) {
if (err) throw err;
 console.log(result.name);
 db.close();
});
});

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

Run "demo_mongodb_findone.js"

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

Which will give you this result: Company Inc.


Find All

To select data from a table in MongoDB, we can also use the find() method.

The find() method returns all occurrences in the selection.


The first parameter of the find() method is a query object. In this example we use an empty query object, which selects all documents in the collection.


No parameters in the find() method gives you the same result as SELECT * in MySQL.


Example

Find all documents in the customers collection:

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.collection("customers").find({}).toArray(function(err, result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});

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

Run "demo_mongodb_find.js"

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

Which will give you this result:

[
 { _id: 58fdbf5c0ef8a50b4cdd9a84 , name: 'John', address: 'Highway 71'},
 { _id: 58fdbf5c0ef8a50b4cdd9a85 , name: 'Peter', address: 'Lowstreet 4'},
 { _id: 58fdbf5c0ef8a50b4cdd9a86 , name: 'Amy', address: 'Apple st 652'},
 { _id: 58fdbf5c0ef8a50b4cdd9a87 , name: 'Hannah', address: 'Mountain 21'},
 { _id: 58fdbf5c0ef8a50b4cdd9a88 , name: 'Michael', address: 'Valley 345'},
 { _id: 58fdbf5c0ef8a50b4cdd9a89 , name: 'Sandy', address: 'Ocean blvd 2'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8a , name: 'Betty', address: 'Green Grass 1'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8b , name: 'Richard', address: 'Sky st 331'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8c , name: 'Susan', address: 'One way 98'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8d , name: 'Vicky', address: 'Yellow Garden 2'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8e , name: 'Ben', address: 'Park Lane 38'},
 { _id: 58fdbf5c0ef8a50b4cdd9a8f , name: 'William', address: 'Central st 954'},
 { _id: 58fdbf5c0ef8a50b4cdd9a90 , name: 'Chuck', address: 'Main Road 989'},
 { _id: 58fdbf5c0ef8a50b4cdd9a91 , name: 'Viola', address: 'Sideway 1633'}
]


Find Some

The second parameter of the find() method is the projection object that describes which fields to include in the result.


This parameter is optional, and if omitted, all fields will be included in the result.


Example

Return the fields "name" and "address" of all documents in the customers collection

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.collection("customers").find({}, { projection: { _id: 0, name: 1, 
address: 1 } }).toArray(function(err, result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});

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

Run "demo_mongodb_find_fields.js"

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

Which will give you this result:

[
 { name: 'John', address: 'Highway 71'},
 { name: 'Peter', address: 'Lowstreet 4'},
 { name: 'Amy', address: 'Apple st 652'},
 { name: 'Hannah', address: 'Mountain 21'},
 { name: 'Michael', address: 'Valley 345'},
 { name: 'Sandy', address: 'Ocean blvd 2'},
 { name: 'Betty', address: 'Green Grass 1'},
 { name: 'Richard', address: 'Sky st 331'},
 { name: 'Susan', address: 'One way 98'},
 { name: 'Vicky', address: 'Yellow Garden 2'},
 { name: 'Ben', address: 'Park Lane 38'},
 { name: 'William', address: 'Central st 954'},
 { name: 'Chuck', address: 'Main Road 989'},
 { name: 'Viola', address: 'Sideway 1633'}
]


You are not allowed to specify both 0 and 1 values in the same object (except if one of the fields is the _id field). If you specify a field with the value 0, all other fields get the value 1, and vice versa:


Example

This example will exclude "address" from the result

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.collection("customers").find({}, { projection: { address: 0 } }).toArray(function(err, result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});

To exclude the _id field, you must set its value to 0:


Example

This example will return only the "name" field:

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.collection("customers").find({}, { projection: { _id: 0, name: 1 } }).toArray(function(err, 
result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});


Example

This example will give you the same result as the first example; return all fields except the _id field:

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.collection("customers").find({}, { projection: { _id: 0 } }).toArray(function(err, result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});


Example

You get an error if you specify both 0 and 1 values in the same object (except if one of the fields is the _id field):


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.collection("customers").find({}, { projection: { _id: 0 } }).toArray(function(err, result) {
if (err) throw err;
 console.log(result);
db.close();
 });
});

The Result Object

As you can see from the result of the example above, the result can be converted into an array containing each document as an object.


To return e.g. the address of the third document, just refer to the third array object's address property:


Example

Return the address of the third document:

console.log(result[2].address); 

Which will produce this result:

Apple st 652

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