Installation

There is a dedicated page in the official documentation for installing MongoDB on Linux, macOS and Windows here.

Create, Show & Delete Database

Unlike in SQL, there is no magical CREATE DATABASE statement to create a database in MongoDB explicitly. Creating a database in MongoDB involves switching to it first using the use statement and inserting at least one document to a collection in it.

To create a database called books, we first switch to it as follows

					
						$ use books
					
				

This however does not create the database yet. You can type the following command to list all the available databases

					
						$ show dbs
					
				

and you will find that only the default test database is listed; the books database which is supposed to be "created" is not there in the list yet. This is because, for a database to be created in MongoDB, you need to save at least one document in a collection.

Now if you need to delete some unwanted database, you can make use of the dropDatabase() method after switching to it as shown here

					
						$ use books
						$ db.dropDatabase()
					
				

Create, Show & Delete Collections

In MongoDB, each database consists of collections, and each collection stores records (actually known as "documents"). Collections are analogous to tables in relational databases. To create a collection, we make use of the createCollection() method.

Below we create a new collection called comics belonging to the books database

					
						$ use books
						$ db.createCollection('comics')
					
				

To list all collections in a books database, you can type the below command

					
						$ use books
						$ show collections
					
				

If you want to remove a collection belonging to some database, chain the drop() method to it as shown here

					
						$ use books
						$ db.comics.drop()
					
				

Create, Query, Update & Delete Documents

It is high time we add some record to our comics collection inside the books database. We add a document consisting of the title, author and year fields with some values.

					
						$ use books
						$ db.comics.insert({
								title: 'Flash Gordon and the Witch Queen of Mongo',
								author: 'Alex Raymond',
								year: 1936
							 })
					
				

All documents inside a collection can be listed chaining the find() method to it

					
						$ use books
						$ db.comics.find()
					
				

Now if you look closely at the result, you will find one _id field automatically indexed. This _id field holds an ObjectId and is the default primary key for a MongoDB document.

If you desire a formatted output, chain the pretty() method to the find() method.

									
						$ db.comics.find().pretty()
					
				

To query a particular document with some field having a specific value, pass the key-value pair as an object to the find() method. Here we query a document with the title field having the value Flash Gordon and the Witch Queen of Mongo

									
						$ db.comics.find({
								"title": 'Flash Gordon and the Witch Queen of Mongo'
							 })
					
				

Suppose you wish to make some changes to the document and update it. Say, you want to change and update its title and year.

									
						$ db.comics.update({"_id":ObjectId("5d43eb866f28a586597cccad")},{
						 	$set:{
								'title':'Flash Gordon and the Ape Men of Mor',
								'year': 1942
							}
						  })
					
				

To remove all documents/records with the title field having the value Flash Gordon and the Ape Men of Mor, run the command

									
						$ db.comics.remove({"title": "Flash Gordon and the Ape Men of Mor"})
					
				

and it will remove all documents with the title Flash Gordon and the Ape Men of Mor in the comics collection.

If you wish to remove just the first occurrence of the document in a collection with the title Flash Gordon and the Ape Men of Mor, pass along 1 as the second parameter.

									
						$ db.comics.remove({"title": "Flash Gordon and the Ape Men of Mor"}, 1)
					
				

If you wish to remove all documents in a collection, you need to pass a pair of empty parentheses to the remove() method.

									
						$ db.comics.remove({})
					
				

Notes

• MongoDB, Inc. offers online courses on MongoDB at MongoDB University for free.