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Introduction To SQL Joins Interview Questions And Answers

SQL refer as Structured Query Language is a language that is designed entirely for accessing databases, and it is the most popular with other Database languages. With SQL, we can create tables, change data, update, and delete as per the business requirement. So, let’s start with the frequently asked SQL joins interview questions.

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Below is the important set of SQL Joins Interview Questions that are divided into two-part:

Part 1 – SQL Joins Interview Questions(Basic)

The first part covers the basic interview questions:

1. What is a SQL join and why do we need it?

SQL joins are used to combine records from two or more than two tables in a database system. A join refers to combining the fields from two or more than two tables by using a value that is common to each of the tables which helps in reducing the repeated columns and data stored in columns of the same table. We need joins to get details about the referenced data and It creates a logical bonding between two or more tables. It is necessary to get data efficiently from multiple tables, that’s why we need SQL joins.

2. What are the different types of SQL joins? Give a brief introduction to them?

There are total 5 joins in SQL, they are: –

a. Inner Join OR Join

This is a kind of join where we get all the records that match the condition in two or more than two tables and then the records in all the tables that didn’t match are not displayed. It displays only the matching entries of two or more tables.

b. Outer Join

If there are no matching columns then it will return NULL values.

This kind of JOIN combines Right Outer Join in addition to Left Outer Join. It displays records from the tables when the conditions are met and displays the NULL value when there is no match.

This kind of join has two conditions, first, it removes duplicates records from the result, and second this join will be made on all the columns with the same name for equality.

This kind of join gives the cartesian product of the two or more than two tables involved.

It is almost the same as the inner join but rather it is a join of a table to itself.

3. What are Nested Joins in SLQ?

This kind of join works for each tuple in the outer join relation, then it scans the entire inner-join relation and adds any tuple that matches the join-condition and the result will be displayed.

Part 2 – SQL Joins Interview Questions (Advanced) 4. What is Merge Join in SQL? 5. What is a hash Join in SQL? how to use it?

The below query is an example of a hash join: –

ORDER BY p.Name, ps. Name

6. How data should be structured to perform Join Operations in a one-to-many relationship and what about a many-to-many relationship?

Generally, one-to-many relationships are structured using a single FOREIGNKEY. Consider our example of customers and orders above:

CREATE TABLE customers ( customer_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, first_name VARCHAR(255) NOT NULL, last_name VARCHAR(255) NOT NULL, email VARCHAR(255) NOT NULL, ); CREATE TABLE orders ( order_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, customer_id INT NOT NULL, order_placed_date DATE NOT NULL, FOREIGN KEY (customer_id) REFERENCES customers (customer_id) );

The answer: we use an intermediary mapping table with two FOREIGN KEYs. Consider the following:

CREATE TABLE orders ( order_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, order_placed_date DATE NOT NULL, ); CREATE TABLE products ( product_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, name VARCHAR(255) NOT NULL, price INT NOT NULL ); CREATE TABLE products_to_orders ( product_to_order_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, order_id INT NOT NULL, product_id INT NOT NULL, FOREIGN KEY (order_id) REFERENCES orders(order_id), FOREIGN KEY (product_id) REFERENCES products(product_id) );

In this example, we need to use two JOIN statements to link all these tables together: one to link products_to_orders to products, and one to link products_to_orders with orders.

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Top 10 Soa Interview Questions And Answers {Updated For 2023}

Introduction to SOA Interview Questions and Answers

Web development, programming languages, Software testing & others

If you are looking for a job related to SOA, you need to prepare for the 2023 SOA Interview Questions. Every interview is indeed different as per the different job profiles. Here, we have prepared the important SOA Interview Questions and Answers, which will help you succeed in your interview.

In this 2023 SOA Interview Questions article, we shall present the 10 most essential and frequently used SOA interview questions. These questions will help students build their concepts around SOA and help them to crack the interview.

Part 1 – SOA Interview Questions (Basic)

This first part covers basic Interview Questions and Answers.

Q1. Explain what SOA governance is and what are its functions.

Service-Oriented Architecture governance is used to control services in any SOA. Some activities are defined as a part of SOA governance. This includes managing a portfolio of services that help plan and develop new services and update the already existing ones. It also includes managing the service lifecycle. This means that all updates of services should not interrupt the current customers and their services. Also, SOA provides consistency of all services by applying rules to all created services. It also offers monitoring services that help the customer know about the downtimes or underperformance of any system, which can be severe for a particular service. As a result, necessary actions can be taken whenever required, and all problems occurring can be instantly resolved by checking performance and availability.

Q2. What are the ends, contract, address, and bindings?

The service can be made available to clients from different ends. All these services must be exposed through one of these ends.

Contract: It is an agreement that is agreed upon between two parties. It defines how clients are expected to communicate. It specifies the different parameters and returns values that are to be used.

Address: This specifies where a user can find a service. There is an address URL that points to the location of services.

Binding: This determines how to access the end. It specifies the process for communication and how it is to be done.

Q3. How can you achieve loose coupling in SOA?

To achieve loose coupling, you can use a service interface like WSDL for a SOAP web service. To limit the dependency, you can hide the service implementation from the consumer. Loose coupling can be handled by encapsulating different functionalities in a way in which it will limit the impact of changes to the implementation of different service interfaces. Also, sometime you may have to change the interface and manage versioning without impacting the customers. Also, one can manage multiple security constraints, multiple transports, and other specifications.

Q4. Are web services and SOA the same?

SOA is an architectural concept, while web services are used to complete them. Web services are the preferred standards that are satisfied to achieve the architectural specifications of SOA. When one uses SOA, all services need to be loosely coupled. Also, SOA services should be able to describe themselves, and WSDL services will be describing how we can access the services. Also, these services can be accessed through WSDL. SOA services are located in a directory, and here UDDI describes where these web services can be found.

Q5. What is a reusable service?

Reusable service is a stateless functionality that has the required granularity. It can be a part of a composite application or composite server. A reusable service should be identified with any activity prescribed by the business and which has its specifications. A service constraint may be security, QoS, SLA or any usage policies. It may be defined by different runtime contracts, multiple interfaces, and different implementations. A reusable service is looked over at the enterprise-level throughout its lifecycle, starting from design time through its runtime. Its reuse should also be promoted through a pre-defined process, and its reuse can be measured.

Part 2 – SOA Interview Questions (Advanced) Q6. Explain Business Layers and Plumbing Layers in SOA. Q8. Explain what the composition of the service is.

By using composition, services are combined to produce composite applications. This application consists of an aggregation of services where an enterprise portal or process is created. A composite service consists of an aggregation of different services which will provide reusable services. It acts like combining electronics components and create reusable composite services.

Q9. What is ESB, and where does it fit in?

ESB stands for Enterprise Service Bus. Unlike other relationships, it provided any to any connectivity between different companies. Also, you may need to consider deployment services, IT services, etc. SOA architecture enables SOA to meet all life’s priorities. The ESB is part of this reference architecture and provides the backbone of an SOA, but it should not be considered an SOA by itself.

Q10. In SOA, do we need to build a system from scratch?

If we need to integrate any existing system, you can only loosely couple wrappers that help wrap all customer services and generically expose all functionalities.

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Top 10 Redux Interview Questions & Answers {Updated For 2023}

Introduction to Redux Interview Questions and Answers

React is a User interface library. The core Redux is built upon action, state, and reducers. All the data resides at the store. Reacts components use actions in order to update the stores. Reducers help the store to update itself. Props make sure the updated stores are available for the React.

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Now Redux is a knowable state container built for JavaScript apps. It allows managing the application state, and it stands to be open source. Applications that run consistently help run in different environments (client, server, and native) and are easy to test.

Now, if you are looking for a job related to Redux, you need to prepare for the 2023 Redux Interview Questions. Every interview is different from the different job profiles, but still, to clear the interview, you need to have a good and clear knowledge of Redux. Here, we have prepared the important Redux Interview Questions And Answers which will help you succeed in your interview.

Below are the 10 important Redux Interview Questions And Answers that are frequently asked in an interview. These questions are divided into two parts are as follows:

Part 1 – Redux Interview Questions (Basic)

This first part covers basic Interview Questions and Answers.

1. Benefits of Redux?


Maintainability: The maintenance of Redux becomes easier due to strict code structure and organization.

Organization: code organization is very strict; hence the stability of the code is high, which intern increases the work to be much easier.

Server rendering: This is useful, particularly to the preliminary render, which keeps up a better user experience or search engine optimization. The server-side created stores are forwarded to the client-side.

Developer tools: It is Highly traceable, so changes in position and changes in the application; all such instances make the developers have a real-time experience.

Ease of testing: The first rule of writing testable code is to write small functions that do only one thing and that are independent. Redux’s code is made of functions that used to be: small, pure, and isolated.

Q2. How Distinct from MVC and Flux?

As far as MVC structure is concerned, the data, presentation, and logical layers are well separated and handled. Change to an application even at a smaller position may involve many changes through the application. this happens because data flow exists bidirectional as far as MVC is concerned. Maintenance of MVC structures are hardly complex, and Debugging also expects a lot of experience for it.

Q3. Functional programming concepts?

The various functional programming concepts used to structure Redux are listed below,

Functions are treated as First-class objects.

Capable of passing functions in the format of arguments.

Capable of controlling flow using recursions, functions, and arrays.

Helper functions such as reduce and map filters are used.

Allows linking functions together.

The state doesn’t change.

Prioritize the order of executing the code is not really necessary.

Q4. Redux change of state?


A function is called in the form of a component.

So now an action gets dispatched by the relative container.

This happens because the prop (which was just called in the container) is tied to an action dispatcher using mapDispatchToProps (in the container).

Reducer on capturing the action, it intern executes a function, and this function returns a new state with specific changes.

The state change is known by the container and modifies a specific prop in the component due to the mapStateToProps function.

Q5. Where can Redux be used?

Redux is majorly used in combination with reacting. It also has the ability to get used to other view libraries too. Some of the famous entities like AngularJS, chúng tôi and Meteor. It can get combined with Redux easily. This is a key reason for the popularity of Redux in its ecosystem. So many articles, tutorials, middleware, tools, and boilerplates are available.

Part 2 – Redux Interview Questions (Advanced) Q6. What is the typical flow of data in a React + Redux app?

Call-back from the UI component dispatches an action with a payload; these dispatched actions are intercepted and received by the reducers. This interception will generate a new application state. From here, the actions will be propagated down through a hierarchy of components from the Redux store. The below diagram depicts the entity structure of a redux+react setup.

Q7. What is store in redux?

ducers return a state via action.

export function configureStore(initialState) { return createStore(rootReducer, initialState); }

The root reducer is a collection of all reducers in the application.

const rootReducer = combineReducers({ donors: donorReducer, }); Q8. Explain Reducers in Redux?

The reducer as follows.

export default function donorReducer(state = [], action) { switch (action.type) { case actionTypes.addDonor: return [...state, action.donor]; default: return state; } }

The reducers receive the initial state and action. Based on the action type, it returns a new state for the store. The state maintained by reducers is immutable. The below-given reducer it holds the current state and action as an argument for it and then returns the next.

state:function handelingAuthentication(st, actn) { return _.assign({}, st, { auth: actn.pyload }); } Q9. Redux workflow features?


Reset: Allow to reset the state of the store

Revert: Rollback to the last committed state

Sweep: All disabled actions that you might have fired by mistake will be removed

Commit: Makes the current state the initial state

Q10. Explain action’s in Redux?

Actions in Redux are functions that return an action object. The action-type and the action data are packed in the action object. Which also allows a donor to be added to the system. Actions send data between the store and the application. The actions produce all information retrieved by the store.

export function addDonorAction(donor) { return { type: actionTypes.addDonor, donor, }; }

Internal Actions are built on top of Javascript objects and associate a type of property to it.

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Top 20 Reactjs Interview Questions And Answers In 2023

ReactJS Interview Questions and Answers

ReactJS is a JavaScript library that is used for building user interfaces. Facebook and an individual group of developers maintain it.

ReactJS is one of the top in-demand skills for web developers, primarily front-end and full-stack developers. As such, a front-end developer earns an average base salary of $129,145 per year. Hence, preparing well for ReactJS interviews can open various job prospects for candidates.

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Key Highlights

ReactJS interview questions involve core concepts such as JSX, state, props, and component lifecycle.

Experience building real-world applications using ReactJS can help demonstrate practical knowledge and problem-solving skills to the interviewer.

Good knowledge of JavaScript and ES6 features is essential to write clean and efficient code while working with ReactJS.

Excellent communication and collaboration skills and a willingness to learn and adapt to new technologies can help make a good impression on the interviewer.

Part 1 –ReactJS Interview Questions (Basic)

This first part covers basic ReactJS Interview Questions and Answers:

Q1. What is React?

Answer: React is a JavaScript library used for building user interfaces. ReactJS is used as a base of a single webpage or mobile application. It deals with the view layer of an application.

Q2. What is JSX?

Answer: JSX is simple JavaScript that allows HTML syntax and other HTML tags in the code. HTML syntax is processed into JavaScript calls of React framework.

Q3. What is FLUX in ReactJS?

Answer: Flux is an application architecture in React View Library that Facebook designed for creating data layers in an application based on JavaScript.

Q4. What are Props and States in React?

Answer: Props mean the arguments’ properties passed in the JavaScript function. A state is used for creating a dynamic and interactive component.

Q5. What are refs in React?

Answer: For focus management and trigger animation, one uses refs in React. It also contains third-party libraries.

Q6. What is the difference between ReactJS and AngularJS?


ReactJS AngularJS

A JavaScript library for building user interfaces. A full-featured JavaScript framework for building large-scale, complex web applications.

It uses a virtual DOM to update the actual DOM efficiently. It uses a two-way data binding approach, where any changes to the model automatically update the view and vice versa.

Follows a unidirectional data flow, where data flows only in one direction, from parent to child components. Follows a bidirectional data flow, where changes in the view automatically update the model, and changes in the model automatically update the view.

It provides more flexibility and control, allowing developers to use any other library or framework alongside it. It provides a complete solution for building web applications, including many built-in features like routing, forms, and animations.

A good understanding of JavaScript is required as it relies heavily on it. It relies more on declarative templates and requires less JavaScript knowledge.

Q7. How is flux different from Redux?


Flux Redux

Flux is an architectural pattern that Facebook introduced. Redux is a predictable state container that is based on Flux architecture.

Flux’s single dispatcher receives actions and dispatches them to the stores. The store receives dispatched actions directly, as Redux has no dispatcher.

Flux has multiple stores that contain the application state. Redux has a single store that contains the entire application state.

Flux stores can have mutable states and be changed anywhere in the application. Redux stores have an immutable state; the only way to change the state is by dispatching an action.

Flux has more boilerplate code and requires more setup. Redux has less boilerplate code and is easier to set up.

Q8. What do you mean by a functional component in React?

Answer: A functional component is a component that returns React elements as an element.

Q9. What is routing?


The ability to switch between various pages or views of an application is called routing in React.

The React Router library implements routing in React applications.

Developers can design routes using essential components and properties because it supports declarative routing.

Routing is integral to building complex React applications, as it allows for better organization and separation of concerns between different parts of an application.

Q10. What are the components of Redux?

Answer: Action, Reducer, Store, and View are the components of Redux.

Action: Describes a user’s intent in the form of an object.

Reducer: A pure function that receives the current state and an action and returns a new state.

Store: A centralized place to store the state of an application.

View: The user interface of an application.

Part 2 –ReactJS Interview Questions (Advanced) Q11. List the characteristics of ReactJS.


JSX: ReactJS has JSX. JSX is simple JavaScript that allows HTML syntax and other HTML tags in the code. The React framework processes HTML syntax into JavaScript calls.

React Native: It contains a native library that supports Native iOS and Android applications.

Simplicity: It is straightforward to grab. Its component-based approach and well-defined lifecycle are direct to use.

Easy to Learn: Anyone with basic programming knowledge can quickly learn ReactJS, for Learning ReactJS, one needs to know the basics of HTML and CSS.

Data-Binding: ReactJS uses one-way data binding and application architecture controls data flow via a dispatcher.

Testability: ReactJS application is straightforward to test. Its views are easy to configure and can be treated as an application.

Q12. What are the lifecycle methods of React Components in detail?

Answer: Some of the most important lifecycles methods are given below:






Q13. What is the lifecycle of ReactJS?


Increased application performance.

Client and Server side building.

Reliable due to JSX code.

Easy testing.

Q15. Which company developed React? When was it released?

Answer: Facebook developed ReactJS and developed it in March 2013.

Q16. What is the significance of the virtual DOM in ReactJS?

Answer: In ReactJS, the virtual DOM is a lightweight copy of the actual DOM, which helps to enhance the application’s performance. Whenever there is a change in the state of a React component, the virtual DOM compares the new and previous states and creates a list of minimum necessary changes. It then updates the actual DOM with these changes, resulting in faster rendering and improved user experience.

Q17. What is the basic difference between pros and state?




Definition Short for “properties,” passed from parent component to child component. User interactions or other events can change a component’s internal state over time.

Immutable Immutable (cannot be modified by the component receiving them) Mutable (can be adjusted using setState())

Update Trigger It can only be updated by the parent component passing in new props. You can update it by calling setState() or forceUpdate() within the component.

Usage Used to pass data from parent to child components. They manage components’ internal state and re-render based on state changes.

Scope It can be accessed throughout the component tree. It can only be accessed within the component where it is defined.

Q18. When to use a class component over a functional component?


Q19. How does one share the data between components in React?


Props: Using props is one method of transferring data from a parent component to a child component. Props are read-only, so the child component cannot alter the data passed through them.

Context: React context offers a mechanism to share data that any component within a specific context can access. It is most beneficial to share data necessary for multiple components, such as user authentication data.

Redux: Redux is a library for state management that offers a universal state store that any component can access. It enables components to dispatch actions to update the shop and subscribe to changes in the shop.

React Query: By caching and controlling the state of asynchronous data, React Query is a data fetching module that offers a mechanism to transfer data between components. Additionally, you can use React to manage the global state.

Local Storage: The ability to store data locally in the browser that may be accessed and shared by components is provided by local storage. We should only use local storage for modest amounts of data, not for confidential or sensitive data.

Q20. What are React hooks? Final Thoughts

Many businesses seek developers with experience in ReactJS, as it has become one of the most widely used JavaScript libraries for creating complex user interfaces. If one is preparing for the ReactJS interview, one should also prepare for JavaScript and must have practical hands-on. Preparing important concepts using interview questions can help one ace their interview.

Frequently Asked Questions (FAQs)

Q1. How do I prepare for a React interview?

Answer: To prepare for a React interview, it’s essential to review the fundamentals of React, including its core concepts, lifecycle methods, and popular tools and libraries. You should also practice building small React applications and be able to explain your approach and decision-making process. Finally, be sure to research the company you’re interviewing with and familiarize yourself with their React-related projects or initiatives.

2. What is ReactJS used for?

Answer: ReactJS is a JavaScript library used for building user interfaces. It allows developers to create reusable UI components and manage the state of an application in a way that is efficient and easy to understand.

3. What questions are asked in interviews on ReactJS?

What is ReactJS?

What is Flux?

How do you define JSX?

What are Props and State?

What are refs?

4. How do you pass React interview questions?

Answer: To pass React interview questions, it’s essential to have a solid understanding of ReactJS’s core concepts and be able to apply them in practical scenarios. It’s also helpful to be familiar with popular React libraries and tools, such as Redux, React Router, and Jest. Practice building small React applications and be prepared to explain your thought process and decision-making. Finally, be confident, communicate clearly, and demonstrate a willingness to learn and adapt.

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Top 100+ Cyber Security Interview Questions And Answers

1) What is cybersecurity?

Here are Cyber Security interview questions and answers for fresher as well experienced candidates to get their dream job.

Cybersecurity refers to the protection of hardware, software, and data from attackers. The primary purpose of cyber security is to protect against cyberattacks like accessing, changing, or destroying sensitive information.

2) What are the elements of cybersecurity?

Major elements of cybersecurity are:

Information security

Network security

Operational security

Application security

End-user education

Business continuity planning

Benefits of cyber security are as follows:

It protects the business against ransomware, malware, social engineering, and phishing.

It protects end-users.

It gives good protection for both data as well as networks.

Increase recovery time after a breach.

Cybersecurity prevents unauthorized users.

4) Define Cryptography.

5) Differentiate between IDS and IPS.

Intrusion Detection System (IDS) detects intrusions. The administrator has to be careful while preventing the intrusion. In the Intrusion Prevention System (IPS), the system finds the intrusion and prevent it.

6) What is CIA?

Confidentiality, Integrity, and Availability (CIA) is a popular model which is designed to develop a security policy. CIA model consists of three concepts:

Confidentiality: Ensure the sensitive data is accessed only by an authorized user.

Integrity: Integrity means the information is in the right format.

Availability: Ensure the data and resources are available for users who need them.

7) What is a Firewall?

It is a security system designed for the network. A firewall is set on the boundaries of any system or network which monitors and controls network traffic. Firewalls are mostly used to protect the system or network from malware, worms, and viruses. Firewalls can also prevent content filtering and remote access.

8) Explain Traceroute

It is a tool that shows the packet path. It lists all the points that the packet passes through. Traceroute is used mostly when the packet does not reach the destination. Traceroute is used to check where the connection breaks or stops or to identify the failure.

9) Differentiate between HIDS and NIDS.

Parameter HIDS NIDS

Usage HIDS is used to detect the intrusions. NIDS is used for the network.

What does it do? It monitors suspicious system activities and traffic of a specific device. It monitors the traffic of all device on the network.

10) Explain SSL

SSL stands for Secure Sockets Layer. It is a technology creating encrypted connections between a web server and a web browser. It is used to protect the information in online transactions and digital payments to maintain data privacy.

11) What do you mean by data leakage?

Data leakage is an unauthorized transfer of data to the outside world. Data leakage occurs via email, optical media, laptops, and USB keys.

12) Explain the brute force attack. How to prevent it?

It is a trial-and-error method to find out the right password or PIN. Hackers repetitively try all the combinations of credentials. In many cases, brute force attacks are automated where the software automatically works to login with credentials. There are ways to prevent Brute Force attacks. They are:

Setting password length.

Increase password complexity.

Set limit on login failures.

13) What is port scanning?

It is the technique for identifying open ports and service available on a specific host. Hackers use port scanning technique to find information for malicious purposes.

14) Name the different layers of the OSI model.

Seven different layers of OSI models are as follows:

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

Application Layer

15) What is a VPN?

VPN stands for Virtual Private Network. It is a network connection method for creating an encrypted and safe connection. This method protects data from interference, snooping, censorship.

16) What are black hat hackers?

Black hat hackers are people who have a good knowledge of breaching network security. These hackers can generate malware for personal financial gain or other malicious reasons. They break into a secure network to modify, steal, or destroy data so that the network can not be used by authorized network users.

17) What are white hat hackers?

White hat hackers or security specialist are specialized in penetration testing. They protect the information system of an organization.

18) What are grey hat hackers?

Grey hat hackers are computer hacker who sometimes violate ethical standards, but they do not have malicious intent.

19) How to reset a password-protected BIOS configuration?

There are various ways to reset BIOS password. Some of them are as follows:

Remove CMOS battery.

By utilizing the software.

By utilizing a motherboard jumper.

By utilizing MS-DOS.

20) What is MITM attack?

A MITM or Man-in-the-Middle is a type of attack where an attacker intercepts communication between two persons. The main intention of MITM is to access confidential information.

21) Define ARP and its working process.

It is a protocol used for finding MAC address associated with IPv4 address. This protocol work as an interface between the OSI network and OSI link layer.

22) Explain botnet.

It’s a number of internet-connected devices like servers, mobile devices, IoT devices, and PCs that are infected and controlled by malware.

23) What is the main difference between SSL and TLS?

The main difference between these two is that SSL verifies the identity of the sender. SSL helps you to track the person you are communicating to. TLS offers a secure channel between two clients.

24) What is the abbreviation of CSRF?

CSRF stands for Cross-Site Request Forgery.

25) What is 2FA? How to implement it for a public website?

TFA stands for Two Factor Authentication. It is a security process to identify the person who is accessing an online account. The user is granted access only after presenting evidence to the authentication device.

26) Explain the difference between asymmetric and symmetric encryption.

Symmetric encryption requires the same key for encryption and decryption. On the other hand, asymmetric encryption needs different keys for encryption and decryption.

27) What is the full form of XSS?

XSS stands for cross-site scripting.

28) Explain WAF

29) What is hacking?

Hacking is a process of finding weakness in computer or private networks to exploit its weaknesses and gain access.

For example, using password cracking technique to gain access to a system.

30) Who are hackers?

A Hacker is a person who finds and exploits the weakness in computer systems, smartphones, tablets, or networks to gain access. Hackers are well experienced computer programmers with knowledge of computer security.

31) What is network sniffing?

Network sniffing is a tool used for analyzing data packets sent over a network. This can be done by the specialized software program or hardware equipment. Sniffing can be used to:

Capture sensitive data such as password.

Eavesdrop on chat messages

Monitor data package over a network

32) What is the importance of DNS monitoring?

Yong domains are easily infected with malicious software. You need to use DNS monitoring tools to identify malware.

33) Define the process of salting. What is the use of salting?

Salting is that process to extend the length of passwords by using special characters. To use salting, it is very important to know the entire mechanism of salting. The use of salting is to safeguard passwords. It also prevents attackers testing known words across the system.

For example, Hash(“QxLUF1bgIAdeQX”) is added to each and every password to protect your password. It is called as salt.

34) What is SSH?

SSH stands for Secure Socket Shell or Secure Shell. It is a utility suite that provides system administrators secure way to access the data on a network.

35) Is SSL protocol enough for network security?

SSL verifies the sender’s identity, but it does not provide security once the data is transferred to the server. It is good to use server-side encryption and hashing to protect the server against a data breach.

36) What is black box testing and white box testing?

Black box testing: It is a software testing method in which the internal structure or program code is hidden.

White box testing: A software testing method in which internal structure or program is known by tester.

37) Explain vulnerabilities in network security.

Vulnerabilities refer to the weak point in software code which can be exploited by a threat actor. They are most commonly found in an application like SaaS (Software as a service) software.

38) Explain TCP Three-way handshake.

It is a process used in a network to make a connection between a local host and server. This method requires the client and server to negotiate synchronization and acknowledgment packets before starting communication.

39) Define the term residual risk. What are three ways to deal with risk?

It is a threat that balances risk exposure after finding and eliminating threats.

Three ways to deal with risk are:

Reduce it

Avoid it

Accept it.

40) Define Exfiltration.

41) What is exploit in network security?

An exploit is a method utilized by hackers to access data in an unauthorized way. It is incorporated into malware.

42) What do you mean by penetration testing?

It is the process of checking exploitable vulnerabilities on the target. In web security, it is used to augment the web application firewall.

43) List out some of the common cyber-attack.

Following are the common cyber-attacks which can be used by hackers to damage network:



Password attacks


Man in the middle


Rogue software

44) How to make the user authentication process more secure?

In order to authenticate users, they have to provide their identity. The ID and Key can be used to confirm the user’s identity. This is an ideal way how the system should authorize the user.

45) Explain the concept of cross-site scripting.

Cross-site scripting refers to a network security vulnerability in which malicious scripts are injected into websites. This attack occurs when attackers allow an untrusted source to inject code into a web application.

46) Name the protocol that broadcast the information across all the devices.

Internet Group Management Protocol or IGMP is a communication protocol that is used in game or video streaming. It facilitates routers and other communication devices to send packets.

47) How to protect email messages?

Use cipher algorithm to protect email, credit card information, and corporate data.

48) What are the risks associated with public Wi-Fi?

Public Wi-Fi has many security issues. Wi-Fi attacks include karma attack, sniffing, war-driving, brute force attack, etc.

Public Wi-Fi may identify data that is passed through a network device like emails, browsing history, passwords, and credit card data.

49) What is Data Encryption? Why it is important in network security?

Data encryption is a technique in which the sender converts the message into a code. It allows only authorized user to gain access.

50) Explain the main difference between Diffie-Hellman and RSA.

Diffie-Hellman is a protocol used while exchanging key between two parties while RSA is an algorithm that works on the basis two keys called private and public key.

51) What is a remote desktop protocol?

Remote Desktop Protocol (RDP) is developed by Microsoft, which provides GUI to connect two devices over a network.

The user uses RDP client software to serve this purpose while other device must run RDP server software. This protocol is specifically designed for remote management and to access virtual PCs, applications, and terminal server.

52) Define Forward Secrecy.

Forward Secrecy is a security measure that ensures the integrity of unique session key in event that long term key is compromised.

53) Explain the concept of IV in encryption.

IV stands for the initial vector is an arbitrary number that is used to ensures that identical text encrypted to different ciphertexts. Encryption program uses this number only once per session.

54) Explain the difference between stream cipher and block cipher.

Parameter Stream Cipher Block Cipher

How does it work? Stream cipher operates on small plaintext units Block cipher works on large data blocks.

Code requirement It requires less code. It requires more code.

Usage of key Key is used only once. Reuse of key is possible.

Application Secure Socket layer. File encryption and database.

Usage Stream cipher is used to implement hardware. Block cipher is used to implement software.

55) Give some examples of a symmetric encryption algorithm.

Following are some examples of symmetric encryption algorithm.



Rijndael (AES)


56) What is the abbreviation of ECB and CBC?

The full form of ECB is Electronic Codebook, and the full form of CBC is Cipher Block Chaining.

57) Explain a buffer overflow attack. 58) Define Spyware.

Spyware is a malware that aims to steal data about the organization or person. This malware can damage the organization’s computer system.

59) What is impersonation?

It is a mechanism of assigning the user account to an unknown user.

60) What do you mean by SRM?

SRM stands for Security Reference Monitor provides routines for computer drivers to grant access rights to object.

61) What is a computer virus?

A virus is a malicious software that is executed without the user’s consent. Viruses can consume computer resources, such as CPU time and memory. Sometimes, the virus makes changes in other computer programs and insert its own code to harm the computer system.

A computer virus may be used to:

Access private data like user id and passwords

Display annoying messages to the user

Corrupt data in your computer

Log the user’s keystrokes

62) What do you mean by Authenticode?

Authenticode is a technology that identifies the publisher of Authenticode sign software. It allows users to ensure that the software is genuine and not contain any malicious program.

63) Define CryptoAPI

CryptoAPI is a collection of encryption APIs which allows developers to create a project on a secure network.

64) Explain steps to secure web server.

Follow the following steps to secure your web server:

Update ownership of file.

Keep your webserver updated.

Disable extra modules in the webserver.

Delete default scripts.

65) What is Microsoft Baseline Security Analyzer?

Microsoft Baseline Security Analyzer or MBSA is a graphical and command-line interface that provides a method to find missing security updates and misconfigurations.

66) What is Ethical hacking?

Ethical hacking is a method to improve the security of a network. In this method, hackers fix vulnerabilities and weakness of computer or network. Ethical hackers use software tools to secure the system.

67) Explain social engineering and its attacks.

Social engineering is the term used to convince people to reveal confidential information.

There are mainly three types of social engineering attacks: 1) Human-based, 2) Mobile-based, and 3) Computer-based.

Human-based attack: They may pretend like a genuine user who requests higher authority to reveal private and confidential information of the organization.

Computer-based attack: In this attack, attackers send fake emails to harm the computer. They ask people to forward such email.

68) What is IP and MAC Addresses?

IP Address is the acronym for Internet Protocol address. An internet protocol address is used to uniquely identify a computer or device such as printers, storage disks on a computer network.

MAC Address is the acronym for Media Access Control address. MAC addresses are used to uniquely identify network interfaces for communication at the physical layer of the network.

69) What do you mean by a worm?

A Worm is a type of malware which replicates from one computer to another.

70) State the difference between virus and worm

Parameter Virus Worm

How they infect a computer? It inserts malicious code into a specific file or program. Generate it’s copy and spread using email client.

Dependency Virus need a host program to work They do not require any host to function correctly.

Linked with files It is linked with any file on a network.

Affecting speed It is slower than worm. It faster compared to a virus.

71) Name some tools used for packet sniffing.

Following are some tools used for packet sniffing.






72) Explain anti-virus sensor systems

Antivirus is software tool that is used to identify, prevent, or remove the viruses present in the computer. They perform system checks and increase the security of the computer regularly.

73) List out the types of sniffing attacks.

Various types of sniffing attacks are:

Protocol Sniffing

Web password sniffing

Application-level sniffing

TCP Session stealing

LAN Sniffing

ARP Sniffing

74) What is a distributed denial-of-service attack (DDoS)?

It is an attack in which multiple computers attack website, server, or any network resource.

75) Explain the concept of session hijacking.

TCP session hijacking is the misuse of a valid computer session. IP spoofing is the most common method of session hijacking. In this method, attackers use IP packets to insert a command between two nodes of the network.

76) List out various methods of session hijacking.

Various methods of session hijacking are:

Using packet Sniffers

Cross-Site Scripting (XSS Attack)

IP Spoofing

Blind Attack

77) What are Hacking Tools?

Hacking Tools are computer programs and scripts that help you find and exploit weaknesses in computer systems, web applications, servers, and networks. There are varieties of such tools available on the market. Some of them are open source, while others are a commercial solution.

78) Explain honeypot and its Types.

Honeypot is a decoy computer system which records all the transactions, interactions, and actions with users.

Honeypot is classified into two categories: 1) Production honeypot and 2) Research honeypot.

Production honeypot: It is designed to capture real information for the administrator to access vulnerabilities. They are generally placed inside production networks to increase their security.

Research Honeypot: It is used by educational institutions and organizations for the sole purpose of researching the motives and tactics of the back-hat community for targeting different networks.

79) Name common encryption tools.

Tools available for encryptions are as follows:




Triple DES

80) What is Backdoor?

It is a malware type in which security mechanism is bypassed to access a system.

81) Is it right to send login credentials through email?

It is not right to send login credentials through email because if you send someone userid and password in the mail, chances of email attacks are high.

82) Explain the 80/20 rule of networking?

This rule is based on the percentage of network traffic, in which 80% of all network traffic should remain local while the rest of the traffic should be routed towards a permanent VPN.

83) Define WEP cracking.

It is a method used for a security breach in wireless networks. There are two types of WEP cracking: 1) Active cracking and 2) Passive cracking.

84) What are various WEP cracking tools?

Well known WEP cracking tools are:





85) What is a security auditing?

Security auditing is an internal inspection of applications and operating systems for security flaws. An audit can also be done via line by line inspection of code.

86) Explain phishing.

It is a technique used to obtain a username, password, and credit card details from other users.

87) What is Nano-scale encryption?

Nano encryption is a research area which provides robust security to computers and prevents them from hacking.

88) Define Security Testing?

Security Testing is defined as a type of Software Testing that ensures software systems and applications are free from any vulnerabilities, threats, risks that may cause a big loss.

89) Explain Security Scanning.

Security scanning involves identifying network and system weaknesses and later provides solutions for reducing these risks. This scanning can be performed for both Manual as well as Automated scanning.

90) Name the available hacking tools.

Following is a list of useful hacking tools.





Angry IP scanner:

Burp Suite


91) What is the importance of penetration testing in an enterprise?

Here are two common application of Penetration testing.

Financial sectors like stock trading exchanges, investment banking, want their data to be secured, and penetration testing is essential to ensure security.

In case if the software system is already hacked and the organization would like to determine whether any threats are still present in the system to avoid future hacks.

Penetration testing cannot find all vulnerabilities in the system.

There are limitations of time, budget, scope, skills of penetration testers.

Data loss and corruption

Down Time is high which increase costs

93) Explain security threat

Security threat is defined as a risk which can steal confidential data and harm computer systems as well as organization.

94) What are physical threats?

A physical threat is a potential cause of an incident that may result in loss or physical damage to the computer systems.

95) Give examples of non-physical threats

Following are some examples of non-physical threat:

Loss of sensitive information

Loss or corruption of system data

Cyber security Breaches

Disrupt business operations that rely on computer systems

Illegal monitoring of activities on computer systems

96) What is Trojan virus?

Trojan is a malware employed by hackers and cyber-thieves to gain access to any computer. Here attackers use social engineering techniques to execute the trojan on the system.

97) Define SQL Injection

It is an attack that poisons malicious SQL statements to database. It helps you to take benefit of the design flaws in poorly designed web applications to exploit SQL statements to execute malicious SQL code. In many situations, an attacker can escalate SQL injection attack in order to perform other attack, i.e. denial-of-service attack.

98) List security vulnerabilities as per Open Web Application Security Project (OWASP).

Security vulnerabilities as per open web application security project are as follows:

SQL Injection

Cross-site request forgery

Insecure cryptographic storage

Broken authentication and session management

Insufficient transport layer protection

Unvalidated redirects and forwards

Failure to restrict URL access

99) Define an access token.

An access token is a credential which is used by the system to check whether the API should be granted to a particular object or not.

100) Explain ARP Poisoning

ARP (Address Resolution Protocol) Poisoning is a type of cyber-attack which is used to convert IP address to physical addresses on a network device. The host sends an ARP broadcast on the network, and the recipient computer responds back with its physical address.

ARP poisoning is sending fake addresses to the switch so that it can associate the fake addresses with the IP address of a genuine computer on a network and hijack the traffic.

101) Name common types of non-physical threats.

Following are various types of non-physical threats:





Denial of Service Attacks

Distributed Denial of Service Attacks


Key loggers

Unauthorized access to computer systems resources


102) Explain the sequence of a TCP connection.

The sequence of a TCP connection is SYN-SYN ACK-ACK.

103) Define hybrid attacks.

Hybrid attack is a blend of dictionary method and brute force attack. This attack is used to crack passwords by making a change of a dictionary word with symbols and numbers.

104) What is Nmap?

Nmap is a tool which is used for finding networks and in security auditing.

105) What is the use of EtterPeak tool?

EtterPeak is a network analysis tool that is used for sniffing packets of network traffic.

106) What are the types of cyber-attacks?

There are two types of cyberattacks: 1) Web-based attacks, 2) System based attacks.

107) List out web-based attacks

Some web-based attacks are: 1) SQL Injection attacks, 2) Phishing, 3) Brute Force, 4) DNS Spoofing, 4) Denial of Service, and 5) Dictionary attacks.

108) Give examples of System-based attacks

Examples of system-based attacks are:





109) List out the types of cyber attackers

There are four types of cyber attackers. They are: 1) cybercriminals, 2) hacktivists, 3) insider threats, 4) state-sponsored attackers.

110) Define accidental threats

They are threats that are accidently done by organization employees. In these threats, an employee unintentionally deletes any file or share confidential data with outsiders or a business partner going beyond the policy of the company.

These interview questions will also help in your viva(orals)

15 Javascript Interview Questions And Answers You Should Know

JavaScript is a popular programming language to build highly engaging websites and apps. It is used by close to 65% of developers, according to Stack Overflow 2023 survey. Most of our prescreened developers at Reintech also rely on the language to woo clients.

Therefore, businesses are always in search of top JavaScript talents to gain a competitive edge. JavaScript developers are also pleased, as they get attractive remuneration and a chance to grow their careers.

However, every JavaScript programmer needs to sit for an interview to get selected. Employers should also utilize the opportunity to assess the skills and capabilities of the developer.

15 JavaScript Interview Questions

Here are some of the best JavaScript interview questions (with answers) to ask when you hire JavaScript developers.

1. What do you mean by event delegation?

Also read: 10 Types of Developer Jobs: IT Jobs

2. What is the use of ECMAScript?

ECMAScript is a standard that puts forward the rules and conditions for any scripting language to be ECMAScript compliant. JavaScript is a scripting language that follows the guidelines of ECMAScript. The standard aims to create interoperability between scripting languages using the rules.

3. When should you use prototypal inheritance?

Prototypal inheritance is a suitable choice where we cannot use functional programming or modules. They allow composition that creates can-do, uses-a, or has-a relations instead of is-a relation developed with class inheritance. Additionally, different types of prototypal inheritance are used for different use cases.

4. What is the use of strict mode in JavaScript?

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5. How can you delete a cookie with JavaScript?

You can delete a cookie in JavaScript by changing the expiration date to one in the past. The process will force the cookie to not return any result if someone tries reading it. In some browsers, it is necessary to define your cookie path to delete it.

6. What is the difference between one-way data flow and two-way data binding?

One-way data flow allows data to move in one direction and makes it easy to comprehend. It also signifies the model is a single source of truth. Additionally, only the model is granted access to manipulate the state of the app.

Two-way data binding indicates the model and data are dynamically bounded. So, any change in model data or UI field affects the other one.

7. What do you mean by higher-order function? Can you give some examples?

A higher-order function returns a chosen function as a return value. Else, it can also accept another function as an argument. Sometimes both are possible. Examples of built-in higher-order functions in JavaScript are reduced, filter, and map.

8. What are the two types of typed language?

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9. What are the benefits of microservice architectures?

Microservices allows an app to run based on several individual applications. It is easy to maintain such architectures as the components are not dependent on one another. Additionally, microservices make your app easier to arrange. We can also make changes to the code easily without affecting the whole app.

10. What is the use of the prompt box? 11. What are the different types of error name values in JavaScript?

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12. How can you embed JavaScript code in HTML files?

We can use several ways to embed JavaScript code in HTML files. One way is to embed them as functions and statements within a

Liza Katiushchenko

Liza Katiushchenko, Digital Marketing and Social Media Manager at Reintech.

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