Node.js MongoDB Find
Thursday 28 June 2018
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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();
});
});
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 an object describing 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({}, { _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({}, { 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({}, { _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({}, { _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({}, { name: 1, address: 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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