MongoDB Basic interview Questions and Answers

1) What is MongoDB ? What are the features and advantages of MongoDB ?

   MongoDB is an free open-source cross-platform documnet-oriented database program.Classified as a NoSQL database program.MonogDB uses JSON-like documents with    schemas.

 Brilliant features and advantages of MongoDB are :

  1) Documnet-oriented

  2) Ad hoc queries

  3) Replication

  4) File storage

  5) Server-side JavaScript execution

  6) Capped collections

  7) Load balancing


2) What are the datatypes in MongoDB ?

   1) String  : String is used to store data.A string must be UTF 8 valid in MongoDB

   2) Integer : Integer is used to store the numeric value.it can be 32 bit or 64 bit its depending up on the server your using

   3) Boolean : Boolean datatype is used to store boolean values.It just shows Yes/No values

   4) Double : Double datatype stores floating point values

   5) Min / Max : This datatype is used to compare a value against the lowest and highest bson values

   6) Arrays : This datatype is used to store a list or multiple values into a single key

   7) Object : Object datatype is used for embedded documents

   8) Symbol : It is generally used for languages that uses a specific type.

   9) Date: This datatype stores the current date or time in unix time format.

3) How to create a database in MongoDB ?

  Synatx: use Database-Name

 Example: >use sequelskillsDB

4) How to check the currently Selected database

    >db

5) How to check the existing database list in MongoDB ?

    >show dbs

6) You created database , if not listed in database list to display database

 >db.examples.insert({"name":"sequelskills"}) 


7)How to Drop a Database in MongoDB ?

 The dropDatabase command is used to drop a database. It also deletes the associated data files. It operates on the current database.

     Syntax:

     db.dropDatabase() 

     Example : 1) >use sequelskillsDB

               2) >db.dropDatabase()


8) How to create a Collection in MongoDB ?

  db.createCollection(name, options) is used to create collection. But usually you don?t need to create collection. MongoDB creates collection automatically when you insert some documents

 Syntax:

  db.createCollection(name, options)

 Example: 1) >use sequelskillsDB

          2) >db.createCollection("SEQUEL")

9) How to check the List of collections in MongoDB ?

    >show collections

10) How does MongoDB create collection automatically ?

    >db.SEQUEL.insert({"name" : "mydocument"})   

   >show collections 

11) How to see/check the inserted document, use the find() command?

  db.collection_name.find()


12) How to Drop MongoDB collection ?

   db.collection.drop() method is used to drop a collection from a database. It completely removes a collection from the database and does not leave any indexes associated with the dropped collections.

       Syntax:

         db.COLLECTION_NAME.drop() 

  Example : 1) >use sequelskillsDB

            2) >db.SEQUEL.drop() 


13) How to create document in MongoDB ?

 db.collection.insert() method is used to add or insert new documents into a collection in your database.

 "db.collection.update()" method and "db.collection.save()" method used for the same purpose


   Syntax

      >db.COLLECTION_NAME.insert(document)

  Example:  >db.SEQUEL.insert({"name" : "mydocument"})

14) How to check the inserted documnet in MongoDB ?

 Synatx: db.collection_name.find()

 Example : db.SEQUEL.find()

15) How to insert the multiple documents in MongoDB ?

 If you want to insert multiple documents in a collection, you have to pass an array of documents to the db.collection.insert() method.

 var alldocuments = 
      [ 
       { 
        Subject: "English", 
        details: { Duration: "6 months", Trainer: "Sonoo Jaiswal" }, 
        Batch: [ { size: "Medium", qty: 25 } ], 
        category: "Programming Language" 
      }, 
      { 
        Subject: "Telugu", 
        details: { Duration: "6 months", Trainer: "Prashant Verma" }, 
        Batch: [ { size: "Small", qty: 5 }, { size: "Medium", qty: 10 }, ], 
        category: "Programming Language" 
      }
    ]; 


     > db.SEQUEL.insert(alldocuments); 


16) How to Update inserted documnet in MongoDB ?

 update() method is used to update or modify the existing documents of a collection.

  Syntax:

   db.COLLECTION_NAME.update(SELECTIOIN_CRITERIA, UPDATED_DATA) 

 Example : >db.SEQUEL.update({'course':'English'},{$set:{'course':'Hindi'}}) 


17) How to Delete a document in MongoDB ?

   the db.colloction.remove() method is used to delete documents from a collection. The remove() method works on two parameters.

  1. Deletion criteria: With the use of its syntax you can remove the documents from the collection.

  2. JustOne: It removes only one document when set to true or 1.

  Syntax:

   db.collection_name.remove (DELETION_CRITERIA) 

 Example : >db.SEQUEL.remove( { type : "programming language" }, 1 )

18) How to Delete a all documnets in MonogDB ?

   >db.SEQUEL.remove({})


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