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();
 
});
});

Run example »

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();
  });
});

Run example »

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();
  });
});

Run example »

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();
  });
});

Run example »

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();
  });
});

Run example »

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();
  });
});

Run example »

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: { name: 1, address: 0
} }).toArray(function(err, result) {
   
if (err) throw err;
    console.log(result);
   
db.close();
  });
});

Run example »

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