Table of Contents
Introduction
MongoDB is a free and open-source NoSQL document database used commonly in modern web applications. In this short tutorial, you'll explore how to work with data in MongoDB. You'll create, retrieve, update, and delete records.
Prerequisites
To complete this tutorial you'll need MongoDB installed, which you can do by following How To Install MongoDB on Ubuntu 18.04.
Creating a Database
On the server running MongoDB, type mongo to open up a connection to the database:
mongo
Once you see the > symbol, you're ready to create your first database and start adding records.
Let's create a personal database to store some data about users.
Our first command use userdb creates a new database with the name of "userdb" you can put whatever name you want in the format use <databasename>.
use userdb
You can verify the database you are currently using with the db command, which in our case returns "userdb":
db
[secondary_label Output]
userdb
Now that your database has been created, you can create some JSON-structured documents to store data in your database.
Execute the following command to insert some data into your database:
db.people.insert({ name: "Andrew", age: 33, hobbies: ["Coding", "Gaming", "Cooking"], hungry: false})
You'll get the WriteResult notification letting you know your insertion was successful:
[secondary_label Output]
WriteResult({ "nInserted" : 1 })
You can use many data-types, including strings, numbers, arrays, and boolean values. The Key doesn't need to have the double quotation marks.
Retrieving Data
Once you have data in your collection, you can start to search and filter that data out using .find(<parameters>)
To verify that your data has been added to the "people" document, use the find() syntax. Execute this command in the MongoDB console:
db.people.find()
This command shows all data that are currently associated with the "people" document.
[secondary_label Output]
{ "_id" : ObjectId("5c08c98f3d828385a2162d94"), "name" : "Andrew", "age" : 33, "hobbies" : [ "Coding", "Gaming", "Cooking" ], "hungry" : false }
If you want to turn this into pretty JSON format, use .pretty() after .find() :
db.people.find().pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08c98f3d828385a2162d94"),
"name" : "Andrew",
"age" : 33,
"hobbies" : [
"Coding",
"Gaming",
"Cooking"
],
"hungry" : false
}
When you add a new record, that Mongo will automatically create an _id key for you to reference at a later time.
Try to add more data and then we'll work on modifying and searching the data.
db.people.insert({ name: "Riley", age: 3, hobbies: ["Sleeping", "Barking", "Snuggles"], hungry: true})
db.people.insert({ name: "You", age: 30, hobbies: ["Coding", "Reading the cloud provider Articles", "Creating Droplets"], hungry: true})
For instance, if I wanted to find only the records of those who are hungry:
db.people.find({ hungry: true }).pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08cbea3d828385a2162d95"),
"name" : "Riley",
"age" : 3,
"hobbies" : [
"Sleeping",
"Barking",
"Snuggles"
],
"hungry" : true
}
{
"_id" : ObjectId("5c08cc2e3d828385a2162d96"),
"name" : "You",
"age" : 30,
"hobbies" : [
"Coding",
"Reading the cloud provider Articles",
"Creating Droplets"
],
"hungry" : true
}
Or by specific hobbies:
db.people.find({ hobbies: "Coding" }).pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08c98f3d828385a2162d94"),
"name" : "Andrew",
"age" : 33,
"hobbies" : [
"Coding",
"Gaming",
"Cooking"
],
"hungry" : false
}
{
"_id" : ObjectId("5c08cc2e3d828385a2162d96"),
"name" : "You",
"age" : 30,
"hobbies" : [
"Coding",
"Reading the cloud provider Articles",
"Creating Droplets"
],
"hungry" : true
}
Updating Data
To modify your data, use the .update() function. but first let's look at our data to see what we want to change:
db.people.find().pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08c98f3d828385a2162d94"),
"name" : "Andrew",
"age" : 33,
"hobbies" : [
"Coding",
"Gaming",
"Cooking"
],
"hungry" : false
}
{
"_id" : ObjectId("5c08cbea3d828385a2162d95"),
"name" : "Riley",
"age" : 3,
"hobbies" : [
"Sleeping",
"Barking",
"Snuggles"
],
"hungry" : true
}
{
"_id" : ObjectId("5c08cc2e3d828385a2162d96"),
"name" : "You",
"age" : 30,
"hobbies" : [
"Coding",
"Reading the cloud provider Articles",
"Creating Droplets"
],
"hungry" : true
}
Modify the name of the third record like this:
db.people.update({ name: "You" }, {$set: { name: "Sammy" }})
The first part of your statement specifies what you are searching for to update, and the second part is the new value you want to set. You'll notice with this command, there was 1 record match, and 1 record modified:
[secondary_label Output]
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
If we now check that record with our newly set name:
db.people.find({ name: "Sammy" }).pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08cc2e3d828385a2162d96"),
"name" : "Sammy",
"age" : 30,
"hobbies" : [
"Coding",
"Reading the cloud provider Articles",
"Creating Droplets"
],
"hungry" : true
}
The name key value has been set to its new value of Sammy.
You can also push new hobbies to the array by using $push instead of $set :
db.people.update({ name: "Sammy" }, {$push: { hobbies: "Typing furiously" }})
db.people.find({ name: "Sammy" }).pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08cc2e3d828385a2162d96"),
"name" : "Sammy",
"age" : 30,
"hobbies" : [
"Coding",
"Reading the cloud provider Articles",
"Creating Droplets",
"Typing furiously"
],
"hungry" : true
}
Now let's look at deleting data.
Deleting Data (D)
Remove data using the .remove() function. You can remove data in a couple of ways, but the safest way is to locate a record to delete by using the unique _id so that, for instance, you have multiple "Sammy" entries, removing by the name: "Sammy" would remove all of them. Let's try this:
db.people.remove({ _id: ObjectId("5c08cc2e3d828385a2162d96")})
[secondary_label Output]
WriteResult({ "nRemoved" : 1 })
db.people.find().pretty()
[secondary_label Output]
{
"_id" : ObjectId("5c08c98f3d828385a2162d94"),
"name" : "Andrew",
"age" : 33,
"hobbies" : [
"Coding",
"Gaming",
"Cooking"
],
"hungry" : false
}
{
"_id" : ObjectId("5c08cbea3d828385a2162d95"),
"name" : "Riley",
"age" : 3,
"hobbies" : [
"Sleeping",
"Barking",
"Snuggles"
],
"hungry" : true
}
The "Sammy" entry has been removed safely, without affecting any other possible "Sammy" records if they were to exist. Try experimenting with this to see what else you can do.
Conclusion
After reading this article, you now have a basic understanding of how to create, retrieve, update, and delete records in a MongoDB database.
