NoSQLnosql with mongo db

 

NoSQL databases also known "not only SQL are non-tabular databases .

NoSQL databases come in a variety of types based on their data model. 

The main types are as follows:

• Document databases store data in documents(BSON) similar to JSON (JavaScript Object Notation) objects. Each document contains pairs of fields and values. The values can typically be a variety of types including things like strings, numbers, booleans, arrays, or objects.

• Key-value databases are a simpler type of database where each item contains keys and values.

• Wide-column stores store data in tables, rows, and dynamic columns

• Graph databases store data in nodes and edges. Nodes typically store information about people, places, and things, while edges store information about the relationships between the nodes.

these types of databases provide the facility to handle a large amount of data and high user loads with ease.

how to show all databases in mongo databases?

show dbs

how to create a database in mongodb?

use database_name

use command will create a new database if it does not exist

example:

use amazon;

but the database does not show the database in the list because there is no collection in the "amazon" database

how to delete a database in mongodb?

db.dropDatabase()

this will delete the current database you are in this is because db represents current database .

 Mongodb stores documents in collections .

A collection exists in a single database. a collection is like a table in RDBMS but these collections are not related.

A collection can store multiple documents.

Note: MongoDB is case-sensitive

how to insert data into a collection?

there are two ways to insert data in a collection:

1.insertOne()

syntax:

db.collection_name.insertOne({key:value,key:value,key:value})

example:

db.student.insertOne( { name: "Sagar", age: 20, marks: 200, subject: "math" }) 

2.insertMany([])

syntax:

db.collection_name.insertMany([

        {

                key:value,

                key:value,

                key:value

        } ,

        {

                key:value,

                key:value,

                key:value

        } ,

        {

                key:value,

                key:value,

                key:value

        } 

])

example:

 db.student.insertMany( [

{

     name: "software", 

     status: true, 

     students: 190 

},

{

     name: "accounting", 

     status: true, 

     students: 130 

 }

])

note: every time you insert a row you will get an object id for each row.

how to show the data inserted in the collection?

syntax:

db.collection_name.find().pretty()

example:

db.student.find().pretty()

how to show the list of all collections created in the database?

show collections

example:

 db.student.find().pretty()

how to delete a collection ?

db.collection_name.drop()

 example:

db.student.drop()

how to show the data of a single row:

you can do that by using find function with key name of the row :

syntax:

db.collection.find({key:value})

example:

 db.employees.find({name:"om"},{_id:0,name:1}).pretty()

limit

syntax:

db.collection_name.find({col_nanme:value}).pretty().limit(no_of_values)

example

db.employees.find({name:"sagar"},{_id:0,name:1}).pretty().limit(1)

skip

syntax:

db.collection_name.find({col_nanme:value}).pretty().limit(no_of_values).skip(no_of_skips)

example:

db.employees.find({name:"sagar"},{_id:0,name:1}).pretty().limit(1).skip(2)

updateOne()

db.collection_name.updateOne(

                                             {     col:value_to_update},

                                                         {

                                                                $set :

                                                                       {

                                                                             key:new_value

                                                                            }

                                                         }    

                                                 })    

example:

db.employees.updateOne({name:"sagar"},{$set :{name:"umesh"}})

updateMany

db.collection_name.updateMany(

                                             {     col:value_to_update},

                                                         {

                                                                $set :

                                                                       {

                                                                             key:new_value

                                                                            }

                                                         }    

                                                 })    

example:

db.employees.updateMany({name:"sagar"},{$set :{name:"umesh"}})

deleteOne

syntax:

db.collection_name.deleteOne({key:value})

example:

db.employees.deleteOne({name:"umesh"})

deleteMany

syntax:

db.collection_name.deleteMany({key:value})

example:

db.employees.deleteMany({name:"umesh"})

drop:

syntax

db.collection_name.drop()

example:

db.employees.drop()

sort:

 apply sort() to the cursor before retrieving any documents from the database.

for ascending order:

db.collection_name.find().sort( { key: 1 } )

for descending order:

db.collection_name.find().sort( { key: -1 } )