MongoDB – Top 10 Most Common Commands for Beginners

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This article represents top 10 most commonly used commands for MongoDB beginners. Please feel free to comment/suggest if I missed to mention one or more important points. Also, sorry for the typos.

Following is the list of these commands:

Following is the list of these commands:

  1. Login into MongoDB: Following command can be used to login into MongoDB database for a particular database. Make sure that the user with credentials such as username and password exists in the database mentioned in place of dbname.
    	mongo -u <username> -p <password> --authenticationDatabase <dbname>
    	
  2. Show all databases: Once logged in as a user with appropriate role as userAdmin or userAdminAnyDatabase, one can see all the databases using command such as show dbs.
  3. Select Database to work with: In order to start working with a particular database, the command such as use databaseName can be executed.
  4. Authenticate and Logout from Database: When switching to different database using use dbName command, one would require to authenticate using a valid database user for that database. Following command can be used for authentication:
    	//
    	// Authenticate
    	//
    	db.auth("username", "password");
    	//
    	// Logout
    	//
    	db.logout()
    	
  5. List Down Collections, Users, Roles etc.: Following commands can be used to check existing collections, users etc.
    	//
    	// List down collections of the current database
    	//
    	show collections;
    	db.getCollectionNames();
    	//
    	// List down all the users of current database
    	//
    	show users;
    	db.getUsers();
    	//
    	// List down all the roles
    	//
    	show roles
    	
  6. Create a collection: Following command can be used to create a collection. The details on this command can be found on this page, Create Collection in a MongoDB database
    	db.createCollection("collectionName");
    	
  7. Insert a Document in a Collection: Once a collection is created, next step is to insert one or more documents. Following is a sample command for inserting a document in a collection.
    	//
    	// Insert single document
    	//
    	db.<collectionName>.insert({field1: "value", field2: "value"})
    	//
    	// Insert multiple documents
    	//
    	db.<collectionName>.insert([{field1: "value1"}, {field1: "value2"}])
    	db.<collectionName>.insertMany([{field1: "value1"}, {field1: "value2"}])
    	
  8. Save or Update Document: Following command, save, can be used to either update an existing document or insert a new one depending upon the document parameter passed to it. In case, the “_id” is passed matching an existing document, the document is updated. Otherwise, a new document is created. Internally, save method uses either insert or update command
    	//
    	// Matching document will be updated; In case, no document matching the ID is found, a new document is created
    	//
    	db.<collectionName>.save({"_id": new ObjectId("jhgsdjhgdsf"), field1: "value", field2: "value"}); 
    	
  9. Display Collection Records: Following commands can be used to retrieve collection records:
    	//
    	// Retrieve all records
    	//
    	db.<collectionName>.find();
    	//
    	// Retrieve limited number of records; Following command will print 10 results;
    	//
    	db.<collectionName>.find().limit(10);
    	//
    	// Retrieve records by id
    	//
    	db.<collectionName>.find({"_id": ObjectId("someid")});
    	//
    	// Retrieve values of specific collection attributes by passing an object having 
    	// attribute names assigned to 1 or 0 based on whether that attribute value needs 
    	// to be included in the output or not, respectively.
    	//
    	db.<collectionName>.find({"_id": ObjectId("someid")}, {field1: 1, field2: 1});
    	db.<collectionName>.find({"_id": ObjectId("someid")}, {field1: 0}); // Exclude field1
    	//
    	// Collection count
    	//
    	db.<collectionName>.count();
    	
  10. Administrative Commands: Following are some of the administrative commands which can be helpful in finding collection details such as storage size, total size, overall statistics.
    	//
    	// Get the collection statistics 
    	//
    	db.<collectionName>.stats()
    	db.printCollectionStats()
    	//
    	// Latency statistics for read, writes operations including average time taken for reads, writes
    	// and related umber of operations performed
    	//
    	db.<collectionName>.latencyStats()
    	//
    	// Get collection size for data and indexes
    	//
    	db.<collectionName>.dataSize() // Size of the collection
    	db.<collectionName>.storageSize() // Total size of document stored in the collection
    	db.<collectionName>.totalSize() // Total size in bytes for both collection data and indexes
    	db.<collectionName>.totalIndexSize() // Total size of all indexes in the collection
    	

     

Ajitesh Kumar

Ajitesh Kumar

Ajitesh is passionate about various different technologies including programming languages such as Java/JEE, Javascript, PHP, C/C++, mobile programming languages etc, and, computing fundamentals related with cloud-native technologies, application security, cloud computing platforms, mobile apps, big data etc.

He has also authored the book, Building Web Apps with Spring 5 and Angular.
Ajitesh Kumar

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