Node.js MongoDB

• Node.js can be used in database applications.

• One of the most popular NoSQL databases is 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 "my_data"

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

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

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("my_data");
                         dbo.createCollection("customers", function(err, res) {
                             if (err) throw err;
                             console.log("Collection created!");
                             db.close();
                        });
                  });

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( ) a 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("my_data");
         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();
         });
     });

Insert Multiple Documents

• To insert multiple documents into a collection in MongoDB, we use the insertMany( ) method.
• The first parameter of the insertMany( ) a 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("my_data");
       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'}
       ];
       dbo.collection("customers").insertMany(myobj, function(err, res) {
         if (err) throw err;
         console.log("Number of documents inserted: " +                       res.insertedCount);
         db.close();
       });
     });

Node.js MongoDB Find

•  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.

Find One

• 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();
  });
});

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