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()