Mongo Db

A database is an organized collection of data that can be easily accessed and managed

Mongo Db is a No SQL database
Mongo Db is a scalable, open-source, high-performance, document-oriented database

Differences

SQL	No SQL
RDBMS - Relational Database Management System	Non-Relational or Distributed
Data stored in tables	Data stored in Collections (like JSON)
Vertically Scalable (Rows will be added vertically)	Horizontal Scalable (Data gets added horizontally)

Setup

Mongod + Compass - link

Mongosh - link

Critical Note

After downloading and installing the Mongo DB. Do the following for windows

Create data folder in the C drive
Create db folder inside data

Server and Client

mongod and mongodb refers to different components of the MongoDB database system:

mongod (server)
- It is the primary daemon process for the MongoDB server. It is responsible for managing the core database system and handling client requests.
- It is the MongoDB server itself, and it runs as a background service or process on a server.
- You typically interact with the MongoDB server through client applications, drivers, and shells.
mongosh (Client)
- It is often used to refer to the MongoDB shell, which is a command-line interface (CLI) tool for interacting with the MongoDB server.
- The MongoDB shell is a JavaScript-based interface that allows you to connect to a MongoDB server, execute database operations, run queries, and perform administrative tasks.
- It is a client-side tool used to communicate with the mongod server.

In summary, mongod is the MongoDB server process responsible for database management and serving client requests, while Mongodb refers to the MongoDB shell, which is a client-side tool for interacting with the server. Both components are essential for working with MongoDB effectively, with mongod handling the server-side operations and mongodb providing a command-line interface for users to interact with the database.

Troubleshoot issues

If you are facing issues in copying and pasting the commands in mongosh command line interface

steps:

1. Open the mongosh command line.
2. Right-click on the command line prompt (On main header Panel)
3. Select Properties.
4. Click on the Layout tab.
5. Check the Use Ctrl + Shift + C/V as Copy/Paste option.
6. Click on the OK button.

Mongo DB Commands

Show all the available dbs
```
 show dbs
```
Create or switch to a new DB
```
 use product
```
Create a collection in the current DB
```
 db.createCollection('prod')
```
To know the current db
```
 db
```
Show all the available collections in the current DB
```
 show collections
```

Add documents (rows) to the collections. Note if there is a collection that doesn't exist earlier then it will create and insert documents.

 db.users.insert({name:'Json', age:'20'}) // Depreciated

 db.users.insertOne({name:'Json', age:'20'})

 db.users.insertMany([{name:'Json', age:'20'}, {name:'octa', age:'24'}])

Drop or delete a collection (books is a collection)
```
 db.books.drop()
```
Drop or delete the current DB
```
 db.dropDataBase()
```
To see all the documents in the collection
```
 db.books.find()
```

To update a document

//Updates one document with given id.
db.books.updateOne(
... { _id: ObjectId("6524317c389043329a67b677") },
... {$set: { name: 'This is just testing book', pages: 400, price: 2000 }} 
... )

//Updates all docs whose pages<600. Price will be incremented by 5
db.books.updateMany(
... {pages:{$lt:600}},
... {$inc:{price:5}}
... )

Operators in mongodb (link)
- Renaming the field (column)

    db.books.updateOne(
    ... {_id: ObjectId("6524317c389043329a67b677")},
    ... {$rename:{name:'bookName'}}
    ... )

Updating the records with new field name which has pages 1000.

    db.books.update( { pages: 1000 }, { $rename: { name: 'bookName' } } )

Increment the value of the field

    db.books.updateOne(
    ... {_id: ObjectId("65243269389043329a67b679")},
    ... {$inc:{price:5}}
    ... )

Updating the records with less than a particular number

    db.books.updateMany(
    ... {pages:{$lt:600}},
    ... {$inc:{price:5}}
    ... )

Deletion

db.books.deleteOne({ _id: ObjectId("65243269389043329a67b679") }) 

db.books.deleteMany({pages: 500})

Formatting the results
```
db.books.find().pretty()
```
Limit the results
```
db.books.find().limit(2)
```
Sorting the results
- Ascending order

    db.books.find().sort({pages:1})

Descending Order

    db.books.find().sort({pages:-1})

Sample usage of selection

db.books.find().limit(2).sort({name:-1})

Query Operators (link)


//equals to 900
db.books.find({price:{$eq:900}})

//Greater than or equals to 900
db.books.find( { price: { $gte: 900 } } )   

//Greater than 900
db.books.find(
... {price: {$gt:900}}
... )

//price between 300 and 900
db.books.find(
... {price: {$in:[300,900]}}
... )

Complex Query

//Find document which has pages 500 and price 105
db.books.find(
... {$and:[{pages:500},{price:105}]}
... )

//Price not greater than 55
db.books.find(
... {price: {$not: {$gt:55}}}
... )

Projections (Show only a few columns or fields) (1-include, 0-exclude)

//This shows the records with name field only with condition price=105
//This also prints _id field by default
db.books.find(
... {price: 105},
... {name:1}
... )

//Show only name field and ignore _id
db.books.find( 
... { price: 105 }, 
... { name: 1, _id: 0 } 
... )

//Don't show name and price fields. All other fields will be shown.
db.books.find(
... {price:105},
... {name:0,price:0}
... )