MongoDB CRUD Operations

MongoDB CRUD Operation:

CRUD stands for
C- create,
R- read,
U-update,
D- delete
Create Operations:
MongoDB has two insert method:

1.db.collection.insertOne()

1. db.collection.insertMany() InsetOne Method:

await db.collection('inventory').insertOne({
  item: 'canvas',
  qty: 100,
  tags: ['cotton'],
  size: { h: 28, w: 35.5, uom: 'cm' }
});

InsetMany Method:

await db.collection('inventory').insertMany([
  {
    item: 'journal',
    qty: 25,
    tags: ['blank', 'red'],
    size: { h: 14, w: 21, uom: 'cm' }
  },
  {
    item: 'mousepad',
    qty: 25,
    tags: ['gel', 'blue'],
    size: { h: 19, w: 22.85, uom: 'cm' }
  }
]);


Read Operations:
Read operations retrieve documents from a collection.
db.collection.find()
Find METHOD:
const cursor = db.collection('inventory').find({
  status: { $in: ['A', 'D'] }
});

Update Operations:
Update operations modify the existing documents in a collection. MongoDB provides the following methods.

1. db.collection.updateOne()
2. db.collection.updateMany()
3. db.collection.replaceOne() UpdateOne Method:

db.collection.updateOne(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>        // Available starting in MongoDB 4.2.1
   }
)

UpdateMany Method:

db.collection.updateMany(
   <filter>,
   <update>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     arrayFilters: [ <filterdocument1>, ... ],
     hint:  <document|string>        
   }
)

Replace One Method:

db.collection.replaceOne(
   <filter>,
   <replacement>,
   {
     upsert: <boolean>,
     writeConcern: <document>,
     collation: <document>,
     hint: <document|string>                   
   }
)

Delete Operations:
Delete operations remove documents from a collection.

1. db.collection.deleteOne()
2. db.collection.deleteMany()

DeleteOne Method:

db.collection.deleteOne(
   <filter>,
   {
      writeConcern: <document>,
      collation: <document>,
      hint: <document|string>        // Available starting in MongoDB 4.4
   }
)

Delete Many Method

db.collection.deleteMany(
   <filter>,
   {
      writeConcern: <document>,
      collation: <document>
   }
)

Relational Database

What is a Relational Database?
A relational database defines database relationships in the form of tables. The tables are related to each other - based on data common to each.

In Above Fig, Structure of the relational database Each box on the figure above contains one table called here the relation of the database.
**

Express.js Hello World Example:

const express = require('express')
const app = express()
const port = 3000
app.get('/', (req, res) => {
  res.send('Hello World!')
})

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`)
})