Trending November 2023 # Top 10 Beneficial Angular 6 Interview Question And Answer In 2023 # Suggested December 2023 # Top 20 Popular

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Introduction to Angular 6 Questions and Answers

Web development, programming languages, Software testing & others

If you are looking for a job related to Angular 6, you must prepare for the 2023 Angular 6 Interview Questions. Every interview is indeed different as per the various job profiles. Here, we have prepared the important Angular 6 Interview Questions and Answers which will help you get success in your interview.

This 2023 Angular 6 Interview Questions article will present the 10 most important and frequently asked Angular 6 Interview questions. These questions are divided into two parts as follows:

Part 1 – Angular 6 Interview Questions (Basic)

This first part covers basic Angular 6 Interview Questions and Answers.

Q1. Provide clear differences with some good examples of code snippets between “declarations”, “providers”, and “imports” in the ng module for angular 6.

Please find below an explanation of the declaration, providers, and imports:

Declarations: This is one of the key features of Angular for available varieties of components or pipes of a single directive for the current module to other directives of the current module. If someone is willing to use some same declared components in the current module from other directives, then the declaration should be made properly.

Imports: Helping with the availability of other module components in a current module by importing the same.

Providers: It is helping DI identify and understand using services and values.

Q2. Explain in detail with a good example of genuine differences identified specifically between “constructor” and “ngoninit” for the angular JS 6 version.

This is the basic Angular 6 Interview Question asked in an interview. Please find a detailed explanation below on the constructor and ngonint for angular JS:

Constructor: Constructor is one of the default declarations for any specific class or object; it can be called every time any class is instantiated, ensuring the initialization of their subclasses and different instance variable fields properly.

Ngonint: It is one of the first initialized methods used by Angular, mentioned in the first component of an angular life cycle. It mainly indicated that angular had been appropriately completed creating the required details. It is not mandatory to use but best practice to use.

Q3. The application developed in Angular 5 is properly working, and I could not find any issue yet. Then why do we plan to upgrade our application to Angular 6? What are the new features introduced with this new version of Angular JS? Explain in detail.

Elements of Angular: One of the key features introduced in Angular 6, is that some of the aspects of Angular can be a wrap and represent one of the web components. The leading utility is the same component can be used efficiently for a non-angular project, as the component can be considered a standard web component.

New Engine for rendering called Ivy: Helping with application performance, especially in increasing speed and decreasing application.

New providers called tree shakable: One of the new ways for registering the provider, add inside the @Injectable() using some new attribute name is providedIn.

RxJS6: One of the updated libraries used by Angular 6.

ElementRef: ElementRef can define separately in the case of Angular 6, not required to use native element property always.

Animation: Angular 6 version introduces one new feature called Animation Builder.

I18n: In Angular 6, we can use i18n at runtime as well; not required to build continuously.

Q4. Explain in detail the reason for using the renderer method in Angular JS, whereas we can easily handle the same by using some native element methods. Was there any facility for using the same? Please explain.

When rendering details and fetching data from the platform, Angular assumes the usage of a single platform and browser. Now if angular is going to use some of the native elements of Angular DOMs, then those elements only can be used for the application of the same DOM environment. In angular 6, one new class has come called Render2, which helps in preparing that native element like and web component element so that it can be used anywhere, avoiding DOM dependency.

Q5. Explain in detail about the compiler used by Angular, called AOT (Ahead of time).

AOT stands for ahead of time. Angular uses it for precompiling all the angular components and available templates during the build process. AOT always launched in angular-based applications more than others.

Part 2 – Angular 6 Interview Questions (Advanced) Q6. One popular key in Angular is Zone; explain the same in detail.

ngZone is nothing but one of the wrappers of the JS file called chúng tôi This key library creates context and ensures proper tracking of various asynchronous functions. Angular is always dependent on zones to detect changes.

Q7. Angular JS developer is sometimes planning to use Lazy loading modules frequently. Explain in detail why it is required and how it impacts directly.

The application will load an expected module based on its demand.

And application start will always be faster than usual.

Let us move to the next Angular 6 Interview Questions

Q8. Explain the lifecycle designed for directives and components in Angular JS, especially for the newly introduced version 6.0.

Below is the lifecycle normally followed by the components and directives of Angular JS:






ngAfterContentInit (only for components)

ngAfterContentChecked (only for components)

ngAfterViewInit (only for components)

ngAfterViewChecked (only for components)

Q9. Is it possible to include one embedded view from a defined templateRef already prepared? If yes, please explain the same.

This is the most asked Angular 6 Interview Question in an interview. The specific utility of TemplateRef uses the createdEmbeddedView method to attach the embedded view to the DOM.

@Component({ selector: 'app-root', template: ` }) export class ApplicationComponent implements AfterViewChecked { constructor() { } ngAfterViewChecked() {, {example: '….'}); } } Q10. Explain in detail if someone is willing to identify the exact route change of Angular then how they can do this.

In Angular 6, there has one option called Rx event, which needs to subscribe to a specific instance of Router. Things can be done by below approaches:

class SomeClass{ Constructor(private route : Router){ } } Recommended Articles

This has been a guide to the list of Angular 6 Interview Questions and Answers. Here we have listed the most useful 10 interview sets of questions so the jobseeker can easily crack the interview. You may also look at the following articles to learn more –

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Top 13 Aws Interview Questions And Answers Updated For 2023

Introduction to AWS Interview Questions and Answers

The following article provides an outline for AWS Interview Questions. Amazon Web Services (AWS) is a comprehensive, on-demand cloud computing platform provided by Amazon to individuals, companies, and government organizations on a paid subscription basis. The technology provides a virtual cluster of a computer that is available all the time via the web. It provides a mix of infrastructure as a service (IaaS), platform as a service (PaaS) and packaged software as a service (SaaS) offerings, and Recovery as a Service (RaaS).

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Hadoop, Data Science, Statistics & others

What is Cloud Computing? Types of Clouds

Public Cloud: A cloud where the third-party service providers make resources and services available to their customers via the internet. Related data and security are with the service providers’ owned infrastructure.

Private Cloud: This is almost similar features as the public cloud, but the data and services are managed by the organization or by the third party only for the customer’s organization. In this type of cloud, major control is over the infrastructure so security-related issues are minimized which makes it different from a public cloud.

Hybrid Cloud: As the name suggests Hybrid, is the combination of both private and public cloud. The decision to choose a type of cloud i.e. private or public usually depends on various parameters like the sensitivity of data and applications, industry certifications and required standards, regulations, and many more.

Understanding Different Types of Cloud Computing

IaaS stands for Infrastructure as a Service. It is the lowest level of a cloud solution and refers to cloud-based computing infrastructure as a fully outsourced service. It provides provision processing, storage, and network connectivity on demand. With the implementation of this service model, the customers can develop their own applications on these resources.

Software as a Service (SaaS), as the name suggests, here the third-party providers provide end-user applications to their customers with some administrative capability at the application level, such as the ability to create and manage their users. Basic customization is possible such as the user can use their own corporate logos, colors, etc.

Security Issues: The Biggest concerns in today’s world: The infrastructure provided by AWS cloud is designed in such a way that ensure flexibility and secure cloud network. It is a scalable and highly reliable platform that enables users to deploy applications and data quickly and securely and thus it is gaining its popularity in today’s market. Security is the major issue in cloud computing. The cloud service providers implement the best security standards and industry certifications, however, storing data and important files on external service providers always a risk.

Technical issues: One of the technical issues that are very common is that if the internet connection is offline then we will not be able to access any of the applications, server, or data from the cloud.

Not easy to switch service providers: It is usually promised that cloud will be flexible to use and integrate, however, switching cloud services is not easy.

Now, if you are looking for a job which is related to AWS then you need to prepare for the 2023 AWS Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important AWS Interview Questions and Answers which will help you get success in your interview.

In this 2023 AWS Interview Questions article, we shall present 10 most important and frequently used AWS interview questions.

These questions are divided into two parts:

Part 1 – AWS Interview Questions (Basic)

This first part covers basic AWS Interview Questions and Answers:

Q1. What are the main components of AWS?


Following are the basic elements of AWS:

Route 53: It is a web service (DNS).

E-mail Service: Provides email service which can be utilized by RESTFUL API or through normal SMTP.

It provides strong protection and identity control services for AWS account.

S3 Services: It’s like warehouse equipment and is a very widely well-known utilized service.

Elastic Block Store (EBS): It provides persistent storage that connects to EC2 to endure data beyond the lifespan of a particular EC2 instance.

Cloud Watch: It is used to observe AWS sources, it also provides facilities by which one can produce a notification alert in the state of crisis.

Q2. What is S3?


S3 stands for Simple Storage Service. It is possible to use S3 services to save and recover the unspecified volume of data, at any time and from everywhere over the web.

Q3. By default how many buckets can be created in AWS?


100 buckets are possible to be created by default for each AWS account.

Q4. In VPC with private and public subnets, where the database servers should ideally be launched (subnet)?


This is the basic AWS Interview Questions asked in an interview. Database servers should ideally be launched with separate subnets, among private and public subnets in VPC.

Q5. List out the components required for Amazon VPC?

Following are the components required for Amazon VPC:

Peering Connection, IG (Internet Gateway), HW VPN Connection, Subnet, Customer Gateway, Router, VPC Endpoint for S3, Virtual Private Gateway, Egress-only Internet Gateway, NAT Gateway.

Q6. How do you safeguard EC2 instances running in VPC?


EC2 instances can be protected by using Security Groups in a VPC. Both INBOUND and OUTBOUND groups can be configured in a Security Group which enables secured access to the EC2 instances. It automatically denies any unauthorized access to the same.

Q7. In a VPC how many EC2 instances can be used?


By default, it is limited to launch 20 EC2 instances at once. However, a maximum of 65,536 instances is possible with VPC.

Part 2 – AWS Interview Questions (Advanced)

This part covers Advanced AWS Interview Questions and Answers:

Q8. What are the different connectivity options present for VPC?


NAT, Internet Gateway (IG), Peering Connections, VPG (Virtual Private Gateway), End Points.

Q9. What are the different types of available Cloud Computing services?


IAAS (Infrastructure as a Service), PAAS (Platform as a Service), SAAS (Software as a Service) etc.

Q10. When a standby Relational Database Service instance is launched will it be available in the same Available Zone?


Q11. What is Lifecycle Hooks?


This is frequently asked AWS Interview Questions asked in an interview. It is used in Auto Scaling. It allows performing custom actions by pausing instances as an Auto Scaling group launches or by terminating them. It is possible to have multiple lifecycle hooks for each auto-scaling group.

Q12. Name two types of Load Balancer?


Application Load Balancer & Classic Load Balancer.

Q13. What is Hypervisor?


Recommended Articles

This has been a guide to the list of AWS Interview Questions and Answers. Here we have listed the top 13 Interview Questions and Answer that are commonly asked in interviews with detailed responses. You may also look at the following articles to learn more –

Top 10 Sql Interview Questions With Implementation

In today’s world, technology has increased tremendously, and many people are using the internet. This results in the generation of so much data daily. This generated data is stored in the database and will maintain it. SQL is a structured query language used to read and write these databases. In simple words, SQL is used to communicate with databases. SQL allows you to perform any database-related task. It is accessible and economical for the majority of organizations. If you plan to give an SQL interview then this article is a must read for you! Checkout the top SQL interview questions

This article was published as a part of the Data Science Blogathon.

Q1. What is common table expression in SQL?

A Common Table Expression (CTE) is a query’s result set that lives temporarily within the execution scope of a statement like SELECT, INSERT, UPDATE, DELETE, or MERGE. The output of a CTE is not kept and only exists while the query is being executed. Making complex queries more readable and simple makes it easier for users to create and maintain them.

The following demonstrates the typical SQL Server syntax for a CTE:

WITH expression_name[(columns [,...])] AS (CTE_definition) SQL_statement;

Use WITH clause to define a common table expression.

In the columns, specify the names of all the columns that need to be retrieved in the CTE

Define CTE after AS that retrieves a table with specified columns.

Finally, write an SQL query using a common table expression.

Let’s see an example to define a Common Table Expression as students_data with id, name, and roll_no columns. And then, a query to return the names of students that starts with the letter A among them.

WITH students_data[(id,name,roll_no)] AS ( SELECT id, name,roll_no FROM students ) SELECT name FROM students_data WHERE name LIKE 'A%'; Q2. How to replace null values with default values in MYSQL?

Sometimes, while using MySQL, you don’t want NULL values to be returned as NULL. But sometimes, you want NULL values to return a different default value. There are some ways in MYSQL to replace these null values with default values.

There are four ways to replace it-

Using IFNULL() function


COALESCE() function

Combination of IF() function and IS NULL operator

Combination of CASE expression and IS NULL operator

Let’s see them one by one.

1. Using IFNULL() function: 

The IFNULL() function takes two expressions and returns the first arguments if the first expression is not null. The second parameter is returned if the first expression returns null.

Let’s see the syntax.

IFNULL(expression, alternate_value) #Example SELECT IFNULL(Name,'N/A') FROM students 2. Using  COALESCE() function: 

The COALESCE() method returns the first non-null arguments from the given list of expressions. The function gives a null result if the expression is empty. Moreover, a specified default value can be used to replace null entries in a table.

Simply, it returns the first non-null argument in the given list of expressions. If there are no non-null values, then NULL is returned.

Let’s see some examples to understand.

SELECT COALESCE('one', 'two', 'three') AS result #result #one SELECT COALESCE(NULL, 'one', 'two', 'three') AS result #result #one SELECT COALESCE(NULL, NULL, 'two', 'three') AS result #result #two SELECT COALESCE('A', NULL, 'B', NULL) AS result #result #A SELECT COALESCE(NULL, NULL, 'P', NULL, 'Q') AS result #result #P SELECT COALESCE(NULL, NULL, NULL, NULL, NULL) AS result #result #NULL 3. Combination of IF() function and IS NULL operator:

We can also use IF() function and IS NULL operator to replace null values with default values. It works like if the value is null, then replace it with a default value; else, return the original expression. Let’s see how it works with some examples.

To replace null values with ‘N/A’ in the names column of a students_data table.

SELECT IF(names IS NULL, 'N/A', names ) AS result FROM students_data 4. Combination of CASE expression and IS NULL operator:

This is almost similar to the previous one. Here we use the CASE operator instead of the IF() function. So first, we will take cases where there is a null value, and then we will replace it with the given default value. Else the original expression will be returned. Let’s take an example to understand in detail.

SELECT CASE WHEN names IS NULL THEN 'N/A' ELSE names END FROM students_data

This code is for the same previous example. To replace ‘N/A’ in the names column when there are null entries.

Q3. What is the SQL Syntax for Auto Increment?


CREATE TABLE table_name ( column_name datatype AUTO_INCREMENT, );

For example,

CREATE TABLE students_data ( id INT AUTO_INCREMENT, name varchar, phone_number INT ); Q4. What are the Different Rank Functions in SQL?

There are four rank functions in SQL





Let’s see them one by one in detail.

1. RANK()

This function will return a number that will be applied to each row in the output partition. Each row receives a rank equal to one plus the rank of the row before it. The RANK function assigns the same rank number to two values that it discovers to be identical within the same partition. The following ranking number will also include duplicate numbers in addition to the preceding rank. As a result, this method does not always assign the ranking of rows in numerical order.

Let’s see the syntax

SELECT column_name RANK() OVER ( PARTITION BY expression ORDER BY expression) AS result FROM table_name; 2. DENSE_RANK()

This is almost similar to that of the rank function. Here also, each row receives rank, adding one to the previous rank. If two rows are identical, then they receive the same rank, and the next row directly receives plus one to the current rank. For example, if the 1st and 2nd rows are identical, then both receive rank 1, and the next third row receives rank 2 instead of rank 3, as in the case of using the RANK() function. That’s the difference.

Let’s see the syntax

SELECT column_name DENSE_RANK() OVER ( PARTITION BY expression ORDER BY expression) AS result FROM table_name; 3.ROW_NUMBER()

The row number function differs from the rank and dense rank functions. Starting from 1, this gives ranks adding 1 to the previous row. No matter if any two rows are identical.

let’s see the syntax

SELECT column_name ROW_NUMBER() OVER ( PARTITION BY expression ORDER BY expression) AS result FROM table_name; 4. NTILE()

The NTILE() function is the one you want to use when you want to distribute groups of rows over a partition evenly. You must tell this ranking function how many groups you want the rows to be equally divided into. According to the specified requirement, each row group receives its rank.

let’s see the syntax

SELECT column_name NTILE(N) OVER ( PARTITION BY expression ORDER BY expression) AS result FROM table_name; Q5. Explain Normalization and Denormalization in SQL.

Normalization removes redundancy from the database, which means it is split across multiple tables instead of just one table. and non-redundant, consistent data is added. An improperly constructed database table is inconsistent and could cause problems when executing operations. Hence database normalization is an important step. An unnormalized table is transformed into a normalized table through this process.

Denormalization is used to aggregate data from several tables into one to be easily queried. Redundancy is added using it. In contradiction to normalization, denormalization reduces the number of tables. Denormalization is used when joins are expensive, and table queries are run frequently. Wastage of memory is the main drawback of denormalization.

Q6. What is the Difference Between SQL and MySQL?

SQLMySQLStands for Structured Query LanguageStands for “My Structured Query Language”Language used for managing relational databasesOpen-source relational database management system (RDBMS)Not a specific database system, but a language implemented by various DBMSsA specific DBMS that utilizes SQL as its query languageProvides a set of commands for creating, modifying, and querying databasesOffers a software platform for creating and managing databasesSupports data storage, retrieval, and manipulation using SQLSupports data storage, retrieval, and manipulation using SQLImplemented by multiple DBMSs such as MySQL, Oracle, PostgreSQL, etc.Developed by MySQL AB, now owned by Oracle CorporationWidely used in various database systemsWidely used in web applications and compatible with multiple operating systemsCan be used with different DBMSs based on the specific implementationCan only be used with the MySQL database management system

Q6. What are the usages of SQL?

Creating and managing databases and their structures.

Inserting, updating, and deleting data within tables.

Querying and retrieving specific information from databases.

Filtering and sorting data based on specific criteria.

Aggregating and summarizing data using functions like SUM, COUNT, and AVG.

Joining multiple tables to combine data from different sources.

Creating views to present customized or filtered perspectives of data.

Implementing constraints to ensure data integrity and enforce rules.

Indexing columns to improve query performance and data retrieval.

Granting and managing user permissions to control access rights and data security.

Q7. What are the different subsets of SQL?

SQL encompasses several subsets or variations that are specific to different database management systems (DBMS) or have specialized purposes. Here are some notable subsets of SQL:

MySQL: SQL variant specific to the MySQL database management system.

PostgreSQL: SQL variant specific to the PostgreSQL database management system.

Oracle SQL: SQL variant specific to the Oracle Database system.

Microsoft T-SQL: SQL variant specific to Microsoft SQL Server, known as Transact-SQL.

SQLite: SQL variant specific to the lightweight, embedded database engine SQLite.

ANSI SQL: The American National Standards Institute (ANSI) SQL is a standardized version of SQL that sets the foundation for most SQL implementations. Different DBMSs may adhere to various versions of ANSI SQL, such as ANSI SQL-92, ANSI SQL:1999, ANSI SQL:2003, etc.

PL/SQL: A procedural extension to SQL used in Oracle Database for creating stored procedures, functions, and triggers.

NoSQL: Although not SQL in the traditional sense, NoSQL databases (e.g., MongoDB, Cassandra, Couchbase) represent a different approach to database management, often focusing on high scalability, schema flexibility, and distributed architectures, and they utilize their query languages that are different from traditional SQL.

Q8. What are some common clauses used with SELECT query in SQL?

When using the SELECT query in SQL, there are several common clauses that can be used to refine and customize the query results. Here are some frequently used clauses:

SELECT: Specifies the columns to be retrieved from the database table(s).

FROM: Identifies the table(s) from which to retrieve the data.

WHERE: Filters the rows based on specified conditions, allowing for data retrieval based on specific criteria.

DISTINCT: Removes duplicate values from the result set, returning only unique values.

ORDER BY: Sorts the result set in ascending (default) or descending order based on one or more columns.

GROUP BY: Groups the result set by one or more columns, often used in conjunction with aggregate functions.

HAVING: Filters the grouped rows based on specified conditions, similar to the WHERE clause but applied after the GROUP BY clause.

LIMIT: Specifies the maximum number of rows to be retrieved from the result set.

OFFSET: Specifies the number of rows to skip from the beginning of the result set before starting to return rows.

JOIN: Combines data from multiple tables based on related columns, allowing for retrieval of data from multiple sources.

UNION: Combines the result sets of two or more SELECT statements into a single result set.

IN: Tests whether a value matches any value in a specified list.

NOT IN: Tests whether a value does not match any value in a specified list.

LIKE: Performs pattern matching to retrieve rows based on specified patterns using wildcard characters.

BETWEEN: Retrieves rows with values within a specified range.

Q9. What is a view in SQL?

In SQL, a view is a virtual table derived from a query’s result. It allows you to encapsulate complex queries into a named, reusable object. A view can be used just like a regular table, enabling you to query its data or perform other operations on it.

Here’s the syntax for creating a view in SQL:

CREATE VIEW view_name AS SELECT column1, column2, ... FROM table_name WHERE condition;

Let’s break down the syntax:

CREATE VIEW view_name: This statement is used to create a view with a specific name, referred to as view_name. You can choose any suitable name for your view.

AS: This keyword indicates that the view definition is starting.

SELECT column1, column2, ...: Here, you specify the columns you want to include in the view. You can select specific columns or use * to select all columns.

FROM table_name: Specifies the table from which you want to retrieve data for the view. You can include joins or subqueries to define more complex queries.

WHERE condition: This part is optional and allows you to include a condition to filter the rows in the view based on specific criteria.

Q10. What is an Index in SQL?

In SQL, an index is a database object that improves the speed of data retrieval operations on database tables. It works like a table of contents, organizing and storing a sorted copy of selected columns from a table. By creating an index on one or more columns, the database engine can locate and retrieve data more efficiently, reducing the need for full-table scans. Indexes enable faster searching, sorting, and joining of data, resulting in improved query performance. However, indexes incur overhead during data modifications (insert, update, and delete operations) as they need to be updated to reflect the changes. Therefore, choose indexes carefully and balance them to optimize database performance.


Social media app users frequently share photographs and posts, which involves databases that can update information and simultaneously display content to millions of users. There are many tables in the database, and each table contains rows of data. SQL helps to maintain these databases. We learned some important topics in SQL in this article.

The media shown in this article is not owned by Analytics Vidhya and is used at the Author’s discretion. 


Core Php Interview Questions And Answers In 2023

Introduction to Core PHP Interview Questions and Answers

Core PHP is actually the meaning of very basic PHP. It is normally used for creating some dynamic web pages for displaying to the end client through their own browser. It has basic core logic of programming on the server side and displays on the client side based on the expected logic.

If you are looking for a job related to Core PHP, you need to prepare for the 2023 Core PHP Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important Core PHP Interview Questions and Answers, which will help you get success in your interview.

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In this 2023 Core PHP Interview Questions article, we shall present the 10 most important and frequently asked Core PHP interview questions. These interview questions are divided into two parts as follows:

Part 1 – Core PHP Interview Questions (Basic)

This first part covers basic Core PHP Interview Questions and Answers.

Q1. Two very common functions used in core PHP for a long time. Those functions include () and require(). Please give some clear differences between including and requiring a function for core PHP.

Include() and require() are both used to include some specific file with the requesting page.

The main difference between them is:

If the developer use requires to include the file, then somehow the process throws some fatal error during execution for unavailability of the file, then execution of the process will entirely stop. But if the developer use includes for including the file, then the entire process will not stop; it will ignore the fatal error and go for executing the next step without stopping the process.

Q2. Suppose we are willing to get the IP address for some client who is using PHP developed web application. Please explain how we can get that IP information in PHP?

There have several options for fetching IP addresses of the client execution machine in PHP. The developer can able to write some critical scripts for fetching those data externally.

But one of the popular and very basic approaches to fetching IP addresses is:


Q3. Explain in detail the difference between the two popular functions of PHP, unset() and unlink().

The main difference between them is:

If the developer used unset() on any file, then that file reference is going to be undefined for the entire application, whereas if the developer mentions one file as unlink, then that file will be removed from the directory and as well as not available for the entire application.

Q4. There are several error types available in PHP. Explain some of the major error types which are very frequently used for PHP applications and give the proper difference of them.

There is the common Core PHP Interview Questions asked in an interview. Several responsibilities normally need to follow by a Core PHP tester in the current IT industry.

Normally in PHP, we are handling three kinds of errors:

Notices: This is just given one notice of wrong coding or execution. It is a very simple and mostly non-critical error that normally occurred script execution time. Suppose an application trying to access some undefined variable; then this kind of notice will come.

Warnings: It is again not that much critical error, but still, any wrong execution warning will be given without stopping the normal execution of the process. An example is, including a function used, but some file is missing in the directory, then the warning will be given, but the process will execute successfully.

Fatal: This is one of the most important errors that came in PHP script execution. It mainly causes the termination of the process by giving a proper explanation. An example is, trying to access some nonexistent object or requiring file uploading, but the file is missing.

Q5. Explain in detail about the difference between GET and POST in the PHP application.

Some of the key differences between GET and POST in PHP are given below:

GET information always passes through a URL, so it is always visible to everyone, whereas POST information is embedded with the request and sometimes it is in the encoded format, so it will not able understandable or visible to the normal user.

GET have some restriction on handling the request, define characters are 2048. Whereas POST doesn’t have this kind of restriction at all.

GET only allows require ASCII data, whereas POST does not have this kind of restriction.

Developer common approach to use Get for fetching data, whereas POST is used for inserting or updating.

Part 2 – Core PHP Interview Questions (Advanced) Q6. Suppose the developer needs to enable some of the error-reporting utilities in PHP. How can it be done, please explain in detail.

Displaying an error message is one of the key requirements, especially in debugging the developer’s error; it normally displays the number of lines of the script where a fatal error got generated. The developer can display this error on the possible page by giving the below command:


But for initializing or activating of displaying error in PHP application, the developer needs to follow any of the below approaches:

Display_error = ON in php.ini

Ini_set(‘display_error’, 1) in the specific script file

Q7. Explain in detail about Traits in the PHP application.

Traits are one of the popular mechanisms specifically for the PHP developer. This mechanism help the developer for allowing to create some reusable code again for the PHP language application in case of those objects where the inheritance objective is not fully supported. In the case of Traits, not possible to inheritance by its own mechanism. It is one of the key requirements that PHP developers should know about the key and powerful features of the language before starting development in PHP.

Q8. Suppose one constant has been defined in one of the PHP scripts. Now developer needs to change that constant value during the execution. Is it possible to do? Explain?

If one value is declared as constant in PHP, then it will never be changed by any process during execution. Therefore, a constant value needs to be assigned at the time of initialization.

Q9. Is it possible to extend one class that is defined as final? Explain?

There are the most popular Core PHP Interview Questions asked in an interview. Some popular test cases in the current IT industry. If the developer defines one class as final, then extending that class is absolutely not possible. If one class or method is declared final then creating a child class and method overloading or overriding both are not possible.

Q10. Explain in detail about _destruct(), and _construct() methods available in PHP classes.

Every PHP object should have two methods called constructor and destructor. Both methods are mainly defined in the build-in. The constructor method is normally called immediately after creating one new instance of the specific class, normally used for initializing all the properties of a class. Whereas the destructor methods are mainly used to release the object of the class from the application memory. The destruction method does not require passing any parameter.

Recommended Articles

This has been a guide to Core PHP Interview Questions. Here we have listed the most useful 10 interview sets of questions so that the jobseeker can crack the interview with ease. You may also look at the following articles to learn more –

Top 10 Hadoop Interview Questions You Must Know


Source: techtarget

HDFS provides the following Five Services:

Name Node: HDFS has just one Name Node named Master Node. The master node can monitor files, operate the file system, and contain all stored data metadata. The name node, in particular, carries information like the number of blocks, the location of the data node where the data is kept, where the replications are saved, and other characteristics. The client has direct communication with the name node.

Secondary Name Node: This is just for taking care of the file system metadata checkpoints that are in the Name Node. This is called the checkpoint node too. It is the Name Node’s helper Node. The Secondary Name Node orders the name node to generate and deliver the fsimage and editlog files, after which the Secondary Name node creates the compacted fsimage file.

Job Tracker: Job Tracker accepts users’ seek for Map Reduce processing. The Job Tracker interacts with the Name Node to determine the location of the data that will be desired in processing. The Name Node responds with the necessary processing data information.

Data Node: A Data Node holds data in the form of blocks. This is named the slave node too, and it is in charge of storing the real data in HDFS, which the client may read and write to. These are daemon slaves. Every 3 seconds, each Data node sends a Heartbeat message to the Name node, indicating that it is alive. When a Name Node does not get a heartbeat from a data node for 2 minutes, it considers that data node to be dead and begins the block replication process on another Data node.

Task Tracker: It is the Job Tracker’s Slave Node, and it will accept the job from the Job Tracker. It gets information from the Job Tracker too. Task Tracker will apply the code to the file. Mapper is the process of applying that code to the file.

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Table of Contents

Q1. How is HDFS Fault Tolerant?

Q2. Write the Features of HDFS.

Q3. Differentiate Between Regular FileSystem and HDFS?

Q4. What are The Most Important Parameters for Configuring a MapReduce Program?

Q5. Name the Three Different Modes in Which Hadoop May Operate.

Q6. What are the Functions of RecordReader, Combiner, and Partitioner in a MapReduce operation?

Q7. How Do You Restart NameNode and all of Hadoop’s Daemons?

Q8. In HDFS, How do you Define Block? What is the Hadoop 1 and Hadoop 2 Default Block Size? Is it Possible to Modify It?

Q9. Contrast HDFS with Network Attached Storage (NAS).

Q10. What Will You do if NameNode Fails?

Q1. How is HDFS Fault Tolerant?


When data is saved on HDFS, NameNode replicates it to several DataNodes. The default replication factor value is 3. You can alter the configuration factor to suit your needs. If a DataNode fails, the NameNode will immediately copy the data from the replicas to another node and make the data available. In HDFS, this provides fault tolerance.

Q2. Write the Features of HDFS.

HDFS has a high fault-tolerance level.

HDFS may be made up of thousands of server computers. Every computer saves a part of the file system data. HDFS identifies and automatically recovers problems that may occur on computers.

HDFS has a high throughput price.

HDFS is intended to store and scan millions of data rows and count or add sections of the data. The length of time necessary for this process is determined by the intricacies involved.

It was created to handle very large datasets in batch-style processes. However, the emphasis is on high data throughput rather than low latency.

HDFS is cost-effective.

HDFS is meant to be constructed on commodity machines and heterogeneous platforms that are low-cost and widely available.

Q3. Differentiate Between Regular FileSystem and HDFS?

Regular FileSystem: In a regular FileSystem, all of the data is kept in one place. Data recovery is difficult due to the machine’s low tolerance for failure. Because seek time is longer, it takes longer to process the data.

HDFS: Data is scattered and managed across several platforms using HDFS. Data can still be retrieved from other nodes in the group if a DataNode fails. Reading takes more time due to the need to read data from the disc locally and coordinate data from multiple systems.

Q4. What are the Most Important Parameters for Configuring a MapReduce Program?

The following configuration parameters are required:

Enter the job’s location in HDFS.

The job’s output location in HDFS

Formats for input and output

Classes with map and reduce functions

The JAR file contains the classes for the mapper, reducer, and driver.

Q5. Name the Three Different Modes in which Hadoop May Operate.

There are three ways in which Hadoop may operate:

Standalone (local) mode: This is the default mode if nothing is configured. All Hadoop elements, like NameNode, DataNode, ResourceManager, and NodeManager, operate as a single Java process in this mode. This makes use of the local filesystem.

Pseudo-distributed mode: A single-node Hadoop deployment is termed a pseudo-distributed Hadoop system. All Hadoop services, including the master and slave services, were run on a single compute node in this way.

Fully distributed mode belongs to Hadoop deployments in which the Hadoop master and slave services operate on distinct nodes.

Q6. What are the Functions of RecordReader, Combiner, and Partitioner in a MapReduce operation?

RecordReader- This interacts with the InputSplit and turns the data into key-value pairs that the mapper can read.

Combiner- This is an optional step that functions like a micro reducer. The combiner accepts data from the map tasks, processes it, and then forwards the results to the reduction phase.

Partitioner- The partitioner determines the number of reduced jobs that will be used to summarize the data. It confirms too, how combiner outputs are routed to the reducer and regulate the important segmentation of intermediate map outputs.

Q7. How Do you Restart NameNode and all of Hadoop’s Daemons?

The following commands will help you in restarting NameNode and all daemons:

Stop the NameNode with the ./sbin/ stop NameNode command and restart it with the ./sbin/ start NameNode command.

You may use the ./sbin/ command to halt all daemons and then restart them using the ./sbin/ command.

Q8. In HDFS, How do you Define Block? What is the Hadoop 1 and Hadoop 2 Default Block Size? Is it Possible to Modify It?

Blocks are the smallest continuous space on your hard disk where data is stored. Each record is kept in a separate “block” on the HDFS, and then those blocks are dispersed around the Hadoop clusters. Files in HDFS are divided into block-sized pieces and stored in separate units.

Hadoop 1 has a 64 MB block size by default.

Hadoop 2 has a 128 MB block size by default.

Yes, blocks may be modified. In a Hadoop context, the chúng tôi option in the chúng tôi file can be used to set the size of a block.

Q9. Contrast HDFS with Network Attached Storage (NAS).

A network-attached storage (NAS) server is a file-level computer data storage server that is linked to a computer network and provides data access to a wide group of customers. NAS can be either hardware or software that provides file storage and access services. Hadoop Distributed File System (HDFS) is a Distributed File System that uses a commodity system to store data.

Data Blocks in HDFS are spread across all machines in a group. NAS, on the other hand, stores data on a specialized system.

HDFS is built to operate with the MapReduce paradigm, which shifts computing to the data. Because data is kept apart from calculations, NAS is unsuitable for MapReduce.

HDFS uses a low-cost commodity system, while NAS is a high-end storage system with a high price tag.

Q10. What Will you do if NameNode Fails?

To get the Hadoop group up and running again, the NameNode recovery process includes the following steps:

Use the file system metadata copy to start a new NameNode (FsImage).

Then, set up the DataNodes and users so that they can identify the newly created NameNode.

After loading the latest checkpoint FsImage (for metadata information) and receiving enough block reports from the DataNodes, the new NameNode will begin serving the client.

However, this NameNode recovery process would potentially be time-consuming on big Hadoop clusters, which becomes much more difficult at the time with normal maintenance. As a result, we use HDFS High Availability Architecture.


The Hadoop Distributed File System (HDFS) is a fault-tolerant data storage file system that works on commodity systems. It was made to solve problems that regular databases couldn’t handle. This page focuses on interview questions for all levels, along with the following points:

Hadoop Distributed File System is shortened to HDFS.

Hadoop Distributed File System (HDFS) and MapReduce are two main elements.

Data stored in a regular FileSystem is preserved in a single system.

A network-attached storage (NAS) server is a computer data storage server that stores files on a network.

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Top 10 Css Books For Beginners And Advanced In 2023

Books to Learn CSS

CSS is used to format the layout and visuals of a markup language, mostly HTML, along with XML documents such as SVG and XUL. This language has become very popular because it saves time and effort when creating and updating multiple web pages with different layouts simultaneously.

Knowing more about the language is imperative as CSS evolves over time. Combining book learning with hands-on practice and exploring online resources is beneficial to stay updated with the latest CSS features and best practices.

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Web development, programming languages, Software testing & others

Key Takeaways

Books explain the various selector types in-depth, including class selectors, ID selectors, attribute selectors, pseudo-classes, and pseudo-elements.

CSS books delve into layout techniques, including the traditional block and inline models, and newer approaches like Flexbox and CSS Grid

Many CSS books touch upon CSS preprocessors like Sass or Less. These preprocessors extend CSS by introducing variables, nesting, mixins, and other valuable features.

Top 10 CSS Books

Here are the top 10 books in no specific order to further your understanding of CSS.

Sr No Books Author Published


1. Head First HTML and CSS: A Learner’s Guide to Creating Standards Elisabeth Robson, Eric Freeman 2012

2. Learn CSS in One Day and Learn It Well LCF Publishing, Jamie Chan 2023

3. CSS in easy steps Mike McGrath 2023

4. CSS Master Tiffany B Brown 2023

5. CSS: The Definitive Guide – Visual Presentation for the Web Eric Meyer, Estelle Weyl 2023

6. CSS in Depth Keith J. Grant 2023

7. CSS Pocket Reference: Visual Presentation for the Web Eric Meyer 2023

8. Modern CSS: Master the Key Concepts of CSS for Modern Web Development Joe Attardi 2023

9. CSS Secrets: Better Solutions to Everyday Web Design Problems Lea Verou 2023

10. CSS Mastery: Advanced Web Standards Solutions Andy Budd, Cameron Moll, Simon Collison 2009

Let us discuss the reviews and takeaways of the CSS Books:-

Book#1: Head First HTML and CSS

Author: Elisabeth Robson, Eric Freeman

Get this Book Here

Book Review

Key Takeaways from that Book

Learn to build blocks, create a new lounge, find a hosting company, etc., to learn more about web development.

Find how the browser works with images, add meta tags, and know overriding inheritance.

Book#2: Learn CSS in One Day and Learn It Well

Author: Jamie Chan

Get this Book Here

Book Review

See complex subject matter concepts broken down into simpler byte-sized vital elements that are easily comprehensible. Practice hands-on examples with suitable illustrations that cater to the need of each learner.

Key Takeaways from that Book

Glance and understand padding and margin properties, Border properties, Navigation bars, and text much better.

Take in applying CSS code, CSS Box model, absolute positioning, etc.

Book#3: CSS in Easy Steps

Author: Mike McGrath

Get this Book Here

Book Review

If you want to bring creative, stylish web pages to the table, then look no more, for here is a book that provides extensive knowledge of the latest style sheet techniques. Access interactive functionality and syntax highlighted code at the touch of your fingers.

Key Takeaways from that Book

Includes getting started in CSS, organizing tables and lists, and generating effects in a simple mannerism.

Manipulate text content, enhance controls of the intuitive web design, and curate beautiful layouts for grids and devices.

Book#4: CSS Master

Author: Tiffany B Brown

Get this Book Here

Book Review

Key Takeaways from that Book

Highlights the importance of complex layouts and bettering repaint and reflow performance penalties.

It provides the best of Flexbox and deep dives into the nitty gritty of using CSS with SVG.

Book#5: CSS: The Definitive Guide

Author: Eric Meyer, Estelle Weyl

Get this Book Here

Book Review

Key Takeaways from that Book

Overview of selectors, line cascade, and old CSS values and units.

Bring colors, gradients, 2D and 3D transforms, container queries, etc.

Reacquaint yourself with padding, borders, and an inline direction layout paradigm.

Book#6: CSS In-depth

Author: Keith J. Grant

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Book Review

Key Takeaways from that Book

Comprises key pointers, technical guidance, insights, and more on topics such as shadows, blends, contrast, etc.

Book#7: CSS Pocket Reference: Visual Presentation for the Web 5th Edition

Author: Eric Meyer

Get this Book Here

Book Review

Key Takeaways from that Book

Contains detailed sections on selectors and queries, structural pseudo-classes, and iteration pseudo-classes.

Learn property references, table layouts, and color values, amongst many more content topics like this.

Book#8: Modern CSS

Author: Joe Attardi

Get this Book Here

Book Review

Key Takeaways from that Book

Covers basic CSS concepts, basic styling, backgrounds, and gradients concisely.

Go through topics like transitions and animations, CSS grid, Responsive design, and transforms.

Create vivid animation elements in your projects with CSS transitions.

Book#9: CSS Secrets: Better Solutions to Everyday Web Design Problems

Author: Lea Verou

Get this Book Here

Book Review

Key Takeaways from that Book

The 47 chapters contain the secrets of daily functional CSS code snippets that use common UI problems and aim to solve them one step at a time.

Book#10: CSS Mastery: Advanced Web Standards Solutions

Author: Andy Budd, Cameron Moll, Simon Collison

Get this Book Here

Book Review

Key Takeaways from that Book

Lays the foundation of the style sheet language, visual formatting model, and image replacement.

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