CRUD MongoDB
Tags: insert, delete, update, query
Published: 2021-12-23 16:35:10

## **CRUD**
In computer programming, **create** , **read** , **update** , and **delete** are the four basic operations of persistent storage. **CRUD** is also sometimes used to describe user interface conventions that facilitate **viewing** , **searching** , and **changing** information using computer-based forms and reports.

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

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

```
 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();
 });
```

## **Second Step Collection**

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

```
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();
  });
});
```



## **Create**

The **first letter of CRUD** , **‘C’** , refers to **CREATE** aka **add** , **insert** . Now insert a document in the "**customers**" collection.To insert a record, or document as it is called in MongoDB, into a collection, we use the **insertOne()** method.

```
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();
  });
});
```


## **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).

```
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();
  });
});
```


## **Delete Document**

To **delete** a record, or document as it is called in MongoDB, we use the **deleteOne()** method. The first parameter of the deleteOne() method is a query object defining which document to delete.

_Delete the document with the address "Mountain 21":_

```
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 myquery = { address: 'Mountain 21' };
  dbo.collection("customers").deleteOne(myquery, function(err, obj) {
    if (err) throw err;
	console.log("1 document deleted");
	db.close();
  });
});
```

## **Update Document**
We can **update** a record, or document as it is called in MongoDB, by using the **updateOne()** method. The first parameter of the **updateOne()** method is a query object defining which document to update.

_Update the document with the address "Valley 345" to name="Mickey" and address="Canyon 123"_

```
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/";
 
MongoClient.connect(url, function(err, db) {
  if (err) throw err;
  var dbo = db.db("mydb");
  var myquery = { address: "Valley 345" };
  var newvalues = { $set: {name: "Mickey", address: "Canyon 123" } };
  dbo.collection("customers").updateOne(myquery, newvalues, function(err, res) {
    if (err) throw err;
    console.log("1 document updated");
    db.close();
  });
});
```

## **Query**
_Filter the Result_
When finding documents in a collection, we can filter the result by using a **query** object. The first argument of the **find()** method is a query object, and is **used to limit the search**.

_Find documents with the address "Park Lane 38"_

```
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 query = { address: "Park Lane 38" };
  dbo.collection("customers").find(query).toArray(function(err, result) {
    if (err) throw err;
	console.log(result);
	db.close();
  });
});
```