AJAX

What is AJAX?

• AJAX = Asynchronous JavaScript And XML.
• AJAX is not a programming language.
• AJAX just uses a combination of:
  • A browser built-in XMLHttpRequest object (to request data from a web server)
  • JavaScript and HTML DOM (to display or use the data)

How AJAX Works

The XMLHttpRequest Object

• All modern browsers support the XMLHttpRequest object.
• Create an XMLHttpRequest Object

ER diagram

What is an ER diagram?

An Entity Relationship (ER) Diagram is a type of flowchart that illustrates how “entities” such as people, objects or concepts relate to each other within a system. ER Diagrams are most often used to design or debug relational databases in the fields of software engineering, business information systems, education and research. Also known as ERDs or ER Models, they use a defined set of symbols such as rectangles, diamonds, ovals and connecting lines to depict the interconnectedness of entities, relationships and their attributes. They mirror grammatical structure, with entities as nouns and relationships as verbs.

Uses of entity relationship diagrams

• Database design
• Database troubleshooting

The components and features of an ER diagram

• Entity
• Relationship
• Attribute
• Cardinality

ERD symbols and notations

 Referance: image :- https://www.smartdraw.com/entity-relationship-diagram/
                     https://stackoverflow.com/questions/1154382/anyone-have-an-erd-symbols-quick-reference 
 More Informations : https://www.lucidchart.com/pages/er-diagrams?a=0

Node.js MongoDB

Now a days all web based application has some database to store the data at the back end.

Nodejs frame work have the ability to work with both relational and non relational database.

Node.js MongoDB 

NoSQL database mongodb quite fame because of its ability to store the any sort of data at any format.In order work we have to download required module.Mongodb required the module to be installed is mongoose.And also with these modules we can perform many operations.Before that we have to get start mongodb in nodejs.

1.Install MongoDB Driver

* We can download from official mongodb driver or open in terminal and execute it

    npm install mongodb

* Node.js used this module to manipulate mongodb database.

  var mongo = require('mongodb');

2.Node.js MongoDB Create Database

To create a database:
1.Create the Mongoclient object

2.Specify the url connection (correct ip address and name of the database want to created)

  i)The first is 'mongodb' which specifies that we are connecting to a mongoDB database.

 ii)The next is 'localhost' which means we are connecting to a database on the local   machine.

 iii)The next is 'EmployeeDB' which is the name of the database defined in our MongoDB database.

3.Connect to our database 

4.Connection established

5.Closing the connection.

To run the database: node EmployeeDB.js

Important:In MongoDB, a database is not created until it gets content!
3.Node.js MongoDB Create Collection

var MongoClient = require('mongodb').MongoClient;

var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {

  if (err) throw err;

  var dbo = db.db("mydb");

  //Create a collection name "customers":

  dbo.createCollection("customers", function(err, res) {

    if (err) throw err;

    console.log("Collection created!");

    db.close();

  });

});

Important: In MongoDB, a collection is not created until it gets content!

4.Node.js MongoDB Insert

By adding console we can check whether that data was inserted or not.

or

To check that the data has been properly inserted in the database, you need to execute the following commands in MongoDB
1.Use EmployeeDB
2.db.Employee.find({Employeeid :4 })
5.Node.js MongoDB Query

Output:

6.Node.js MongoDB Insert

7.Node.js MongoDB Update

8.Delete Document

For small exercise refer:
https://github.com/sorubys/nodemongo/blob/master/sivasorubynodemongoex2.pdf

https://github.com/sorubys/nodemongo/blob/master/sivasorubynodemongoex2ii.pdf