How to Rename Document field in MongoDB and $rename Operator

 Sometime We want to Rename the Document field in Collection MongoDB using $rename Operator. Again by using collection method we can do it easily. whenever we want to rename the document field we have to use $rename operator.

db.collectionName.update( criteria, objNew, upsert, multi )

Criteria : This will hold the criteria for updating the document. Here you can specify the condition whether you want to update all the document or few document in collection.

objNew :  $operator which will manipulate the object.

upsert : It is Upsert Operation which will insert the record if it doesn't exist.

multi : Indicates matched documents criteria should be updated or just one Document.

---

MongoDB Rename Document field

Step 1 :  Create DB and Collection

Create studentInfo DB in mongoDB using below command as well as create student collection and insert Document in it.

  

                       

Now we will have some document sample from student collection. By using below query we will fetch document.

db.student.find().pretty()

Output of Above query is below.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1,
        "exam_status" : "PASSED"
}

Rename the Document field "name" as "fullName"

In the above document we will rename the field "name" using below query which uses $rename operator to do that.

db.student.update({},{$rename :{"name":"fullName"}}, false, true)

This above query will rename the document filed. after executing this we will fetch the document again. Output is below.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1,
        "fullName" : "M Kumar"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1,
        "exam_status" : "PASSED",
        "fullName" : "MOHAMMED ISHAQ  H"
}

Add a new field to all documents in a collection in MongoDB

Sometime You want to add new fields in existing document in MongoDB collection. You must follow this. Lets Start with example and we will add the new field in the document.

Adding new Field in Existing Document Collection

Create studentInfo Database in MongoDB server. Use the below code for creating the DB. Use db.createCollection("collection-Name")  and create student Collection and insert Document in mongoDB.

  

                       

Insert Some Document in student collection where further we can apply the MongoDB Collection Methods to add new field in existing document in student Collection. Inserted document in student Collection. Below is the document list present in student collection.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "id" : 4,
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08",
        "marks" : 43,
        "created_at" : "2012-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebf58376803d36568082c60"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

Add New fields in existing Document in Collection

Syntax for Update method in MongoDB is below. By using the below customize code we will add new field in document.

db.collection.update( criteria, objNew, upsert, multi )

Criteria : This will hold the criteria for updating the document. Here you can specify the condition whether you want to update all the document or few document in collection.

objNew :  $operator which will manipulate the object.

upsert : It is Upsert Operation which will insert the record if it doesn't exist.

multi : Indicates matched documents criteria should be updated or just one Document.

Adding  new field in the student Collection

Now we will Add new Field named status in student Collection document and set the value to 1. Below is the code for your reference.

db.student.update({}, {$set :{"status": 1}}, false, true)

Above command will add the new field in existing document of Student Collection. Run the command and again fetch the document using find() method you will see that all the document got updated with status filed.

db.student.find().pretty()

All the document have the new field named with status and value is assigned to 1.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "id" : 4,
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08",
        "marks" : 43,
        "created_at" : "2012-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebf58376803d36568082c60"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}

Add new Filed exam_status as Pass in Document if marks > 60

Query to add new field exam_status as pass if the marks greater then 60. Below is the code which will add new fields in student collection. 

db.student.update({marks : {$gt :60}}, {$set :{"exam_status" : "PASSED"}}, false, true)

this above query will add the exam_status field  with value pass if  the marks is greater then 60. check the below code and the output.

db.student.find().limit(3).pretty()

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1,
        "exam_status" : "PASSED"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42",
        "isOpen" : false,
        "status" : 1,
        "exam_status" : "PASSED"
}

MongoDB Aggregate Query and Aggregation Pipeline Operator

MongoDB Aggregation Pipeline Operator

We will perform all the mongoDB Aggregation Operator on studentInfo DB. Create studentInfo Database in MongoDB server. Use the below code for creating the DB.

  

Insert Some Document in student collection where we can apply the MongoDB Collection Methods to explore further usage. Inserting five document in Student Collection. Below is the document list present in student collection.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "id" : 4,
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08",
        "marks" : 43,
        "created_at" : "2012-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebf58376803d36568082c60"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

Aggregation Pipeline Stages

MongoDb Aggregation purpose is to process the data to get the computed Result. For executing that we use db.collectionName.aggregate() method.

Aggregation Syntax is     db.collectionName.aggregate( [ { <stage> }, ... ] )

$toLower() Aggregate Function

$toLower function in mongoDB convert the given strings in lower case and return the result. Below is the code for your Reference purpose.

db.student.aggregate([{$project :{name :{$toLower:"$name"}}}])

As above code will convert the document name field in lower case. Below is the output.

{ "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"), "name" : "m kumar" }
{ "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"), "name" : "mohammed ishaq  h" }
{ "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"), "name" : "anbuselvam s" }
{ "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"), "name" : "martinpriyadoss j" }
{ "_id" : ObjectId("5ebf58376803d36568082c60"), "name" : "jagan j" }

---

$toUpper() Aggregate Function

MongoDB Find and FindOne Collection and Shell Method

We will perform all the mongoDB Shell collection methods on studentInfo DB. Create studentInfo Database in MongoDB server. Use the below code for creating the DB.

 

Using db.createCollection() method, create collection in database. Command to create studnet collection in studentInfo Database is below 

Insert Some Document in student collection where we can apply the MongoDB Collection Methods to explore further usage. I am Inserting five document in Student Collection.

Mongo Findone Shell Collection Method

Above Image contain the document in student collection. We will use student Collection from studentInfo DB to execute our Find One Mongo Methods. We will use pretty() function at the end of all the collection to get the output in parse format.

• db.collectionName. find()
• db.collectionName. findOne()
• db.collectionName. findAndModify()
• db.collectionName. findOneAndDelete()
• db.collectionName. findOneAndReplace()
• db.collectionName. findOneAndUpdate()

⇛ db.student.find().pretty() :-

This above MongoDB Shell find Query will return all the document present in the Student Collection without filtering anything.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf55"),
        "id" : 2,
        "name" : "MOHAMMED ISHAQ  H",
        "dob" : "2002-06-14",
        "marks" : 67,
        "created_at" : "2016-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "id" : 4,
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08",
        "marks" : 43,
        "created_at" : "2012-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebf58376803d36568082c60"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

⇛ db.student.findOneAndDelete({name:"JAGAN J"})

This above query will find the document in which document.name will be equal to "JAGAN J" and it will delete that particular record and return the deleted document.

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

⇛ db.student.findOne()

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}

db.collectionName.findOne() method will return the first matching record from the document collection.

⇛ db.student.find({name:"M Kumar"}).forEach(printjson)

{

        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "id" : 1,
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54,
        "created_at" : "2017-11-13 23:33:42"
}

⇛ db.student.find({name:"M Kumar"},{name:1,dob:1,marks:1}).pretty()

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf54"),
        "name" : "M Kumar",
        "dob" : "2003-04-07",
        "marks" : 54
}

Note :- Find() shell Collection Method will pull all the collection document fields. If you want some certain collection field then you have to pass the field-name : 1 as the second parameter. Example code is above for reference.

Logical Operator and Filter on FindOne Shell Method

⇛ db.student.findOne({marks :{$lt:50}},{name:1,dob:1})

{
        "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
        "name" : "MARTINPRIYADOSS J",
        "dob" : "2004-03-08"
}

⇛ db.collection.find({$or:[{marks :{$gt:70}},{name:"JAGAN J"}]}).pretty()

{
        "_id" : ObjectId("5ebea4f850845b5c0ea8bf51"),
        "id" : 3,
        "name" : "ANBUSELVAM S",
        "dob" : "2004-06-18",
        "marks" : 87,
        "created_at" : "2019-11-13 23:33:42"
}
{
        "_id" : ObjectId("5ebea4f850845b5c0ea8bf53"),
        "id" : 5,
        "name" : "JAGAN J",
        "dob" : "2003-04-10",
        "marks" : 98,
        "created_at" : "2012-11-13 23:33:42"
}

MongoDB Crud Operation and Mongo DB Crud

MongoDB Crud Operation Basics

Create studentInfo Database in MongoDB server. Use the below code for creating the DB.

Above use studentInfo command will create the DB in MongoDB Server. If studentInfo DB will exist then it will switch to that instead of creating it. To view the created database in the list you must have to create at least one collection in that.

MongoDB provide db.createCollection() method to create collection in database. Command to create studnet collection in studentInfo Database is below 

Press Enter collection will be created in studentInfo Database with the name of student. To view all the collection in the studentInfo Database use below command. Below command will list all the collection present in the studentInfo Database. 

Insert or Create Document in MongoDb Collection

To insert document in the collection in MongoDB Database. We use below two command to insert the document.

• db.collectionName.insertOne()
• db.collectionName.insertMany()

Using above two method we will insert the document in the student Collection of studentInfo Database. 

This below command will insert one document in student Collection.

db.student.insertOne(
   { 
     "id":1,
     "name":"Manoj Kumar",
     "dob":"2003-04-07",
     "marks":54,
     "created_at":"2017-11-13 23:33:42"
   }
)

To Insert many document at a time we have to use db.collectionName.insertMany() method . Below is the code for inserting many document at a time. We can pass all the document as a array.

db.student.insertMany([
   { 
     "id":2,
     "name":"MOHAMMED  H",
     "dob":"2002-06-14",
     "marks":67,
     "created_at":"2016-11-13 23:33:42"
   },
   { 
     "id":3,
     "name":"ANBUSELVAM S",
     "dob":"2004-06-18",
     "marks":87,
     "created_at":"2019-11-13 23:33:42"
   }
 ])

---

Fetch Or Retrieve Document from Collection

To retrieve or fetch the document from the MongoDB collection we use db.collectionName.find() method.

• db.student.find() method will fetch all the document from the specified MongoDB collection. This above method will fetch all the document in single line which will not be in readable format.
• db.student.find().pretty() method will fetch and arrange the collection document in some proper readable format. pretty() method will give you the output is below for reference. 
• 

MongoDB Operators and Query Example

We can apply various filter on mongoDB collection document based on certain condition. We can use various operator also for document filter. Below is the query list and condition to demonstrate the filtration.

$eq (=)	$eq will match the value with specified value.
$gt (>)	$gt will check that the value is greater than specified value.
$gte (>=)	$gte will check that the value is greater than equal to specified Value.
$in (IN)	$in will check that specified value is there in range or not.
$nin (NOTIN)	$nin will check that specified value not lies in the range.
$lt (<)	$lt will check that the value is less than the specified value
$lte (=<)	$lte will check that the value is less than the specified value
$ne (!=)	$ne will check whether the value not equal to specified value

$and	Logical AND join multiple query clause and compare multiple clause and return value as True or False.
$not	Logical NOT Check the query expression and return the result.
$nor	Logical NOR join multiple query clause and compare multiple clause
$or	Logical OR  join multiple query clause and compare multiple clause and return value as True or False

Some Query Example using above operator is below for reference with output.

•  db.student.find({marks:{$eq:43}}).pretty()     O/P is below                                                                                             
  

• db.student.find({marks :{$gte:70}}).pretty()  O/P is below                                                                                 
  

• db.student.find({marks :{$in:[54, 87]}}).pretty()  O/P is below                                                                         
  

Query Using AND Logical Operator in MongoDB

• db.student.find({$and :[{name : "JAGAN J"},{marks :98}]}).pretty()                                               {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
      }

Query Using OR Logical Operator in MongoDB

• db.student.find({$or :[{name:"JAGAN J"},{marks :{$gt:70}}]}).pretty()                                     {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf56"),
          "id" : 3,
          "name" : "ANBUSELVAM S",
          "dob" : "2004-06-18",
          "marks" : 87,
          "created_at" : "2019-11-13 23:33:42"
  }
  {
          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
  }

Query Using AND Operator as well as OR in MongoDB

• db.student.find({marks :{$lt : 99}, $or :[{marks :{$in:[43,98]}},{name : "JAGAN J"}]}).pretty()                                                                                                                                  {

          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf57"),
          "id" : 4,
          "name" : "MARTINPRIYADOSS J",
          "dob" : "2004-03-08",
          "marks" : 43,
          "created_at" : "2012-11-13 23:33:42"
  }
  {
          "_id" : ObjectId("5ebeaafd50845b5c0ea8bf58"),
          "id" : 5,
          "name" : "JAGAN J",
          "dob" : "2003-04-10",
          "marks" : 98,
          "created_at" : "2012-11-13 23:33:42"
  }

MongoDB Update Query

Update query in MongoDB is done using below method.

• db.collection.updateOne() 
• db.collection.updateMany() 
• db.collection.replaceOne()

Delete Operation In MongoDB

Delete Query in MongoDB is done using below method.

• db.collection.deleteOne() 
• db.collection.deleteMany()