Showing posts with label MongoDB Query. Show all posts

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"
}

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()

MongoDB Basic Command and noSql Query

MongoDB is document based NoSql Database written in C++.

Before Learning MongoDB we must have the basic idea of SQL vs NoSqL.

Difference Between SQL and NOSQL

SQL(Structured Query Language)

SQL database is primarily known as RDBMS (Relational Database Management System) which is table based Database. Data is Stored in Table.
SQL database is vertically Scalable. Oracle, Postgres, MsSql etc is example of RDBMS.

NOSQL

NOSQL database is primarily known as Non Relational Database or distributed Database which store the data in the form of document or key value pair etc.
NOSQL is Horizontally scalable, MongoDB, Redis, NEO4J is NOSQL Database Example.

Before Using MongoDB You must know the basic command to run, View and execute the query on command prompt. First Install the MONGODB Server.

Command to run the MongoDB Server

➥ mongod (Type this Command and press Enter)

To Check the Version of MongoDB Installed

➥ mongo --version (Type this Command and press Enter)

To Start the MongoDB Type the Command in Cmd Prompt

➥ mongo (Type this Command and press Enter)

Command to Create DB in Mongo

➥ use db-name (db-name can be anything Type this Command and press Enter)

To Check the Status of Created Database In MongoDB

➥ show dbs ( Type this Command and press Enter)

Note : Once we use the above command to know the status of Database creation. Our newly created database will not come in the list because it do not contain any collection.

So Once you create the Database in MongoDB create few collection in that then by using ➥ show dbs command you can see the DB created by you in the list. Once you create the collection you can view the list of Database.

To use particular DB from the list use this command, by default test DB is used.

➥ use db-name ( Type this Command and press Enter)

Command to know the current DB which is used

➥ db ( Type this Command and press Enter)

How to create the collection in MongoDB

Command to Create the collection in MongoDB

➥ db.createCollection(" Collection-Name ") ( Type this Command and press Enter)

Command to Show all the collection Created In Mongo Database

➥ show collections ( Type this Command and press Enter)

How to Drop the collection From The MongoDB

➥ db.collection-name.drop() ( Type this Command and press Enter)

How to Drop any Database created in MongoDB

Top 100 Question and Answer with Explanation