NODE JS QUESTION ANSWER
Published: 2021-12-23 05:30:17

                            
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1.What are CRUD operators?
CRUD is an acronym that stands for Create, Read, Update, and Delete. These are the four most basic operations that can be performed with most traditional database systems and they are the backbone for interacting with any database.
 
CRUD (create, read, update, delete) is an acronym that refers to the four functions we use to implement persistent storage applications and relational database applications, including the Oracle Database, Microsoft SQL Server, and MySQL.
 
2.What is JWT ?
JWTs can be used as an authentication mechanism that does not require a database. The server can avoid using a database because the data store in the JWT sent to the client is safe.
JWT, or JSON Web Token, is an open standard used to share security information between two parties — a client and a server. Each JWT contains encoded JSON objects, including a set of claims. JWTs are signed using a cryptographic algorithm to ensure that the claims cannot be altered after the token is issued.
 
 
3.How do work  Mongoose ?
Mongoose is a JavaScript library that allows you to define schemas with strongly typed data. Once a schema is defined, Mongoose lets you create a Model based on a specific schema. A Mongoose Model is then mapped to a MongoDB Document via the Model's schema definition
It takes 3 arguments and they are query (also known as a condition), query projection (used for mentioning which fields to include or exclude from the query), and the last argument is the general query options (like limit, skip, etc).
4. How is it work Relational database (MySql) ?
A relational database organizes data into tables which can be linked—or related—based on data common to each. This capability enables you to retrieve an entirely new table from data in one or more tables with a single query.
Like most database management systems out there, MySQL has a client-server architecture and can be used in a networked environment. The server program resides on the same physical or virtual system where the database files are stored, and it is responsible for all interactions with the databases.
5.What is  Aggregation ?
In database management, an aggregate function or aggregation function is a function where the values of multiple rows are grouped together to form a single summary value.
 

In aggregation, relationship with its corresponding entities is aggregated into a higher level entity. For example: Center entity offers the Course entity act as a single entity in the relationship which is in a relationship with another entity visitor.
 
 
 
6.How do work  Express ?
Express is middleware-based : It basically funnels incoming requests through a chain of middlewares (of steps) where we can do something with the request, read some data from it, manipulate it, check if the user is authenticated or basically send back a response immediately.
 
 7.What is node and why it is used?

Node. js is a platform built on Chrome's JavaScript runtime for easily building fast and scalable network applications. Node. js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. Node.