Xetech Interview Questions and Answers

Clustered index physically reorders the data in the table while non-clustered index creates a separate structure.

• Clustered index determines the physical order of data in the table, while non-clustered index does not.

• A table can have only one clustered index but multiple non-clustered indexes.

• Clustered index is faster for retrieval of data but slower for insert and update operations.

• Non-clustered index is slower for ret...read more

Redux is a state management tool for React Native, while Saga is a middleware for handling side effects.

• Redux is used to manage the state of the application in a predictable way.

• Saga is used to handle side effects like asynchronous calls and impure functions.

• Redux and Saga are often used together in React Native applications to manage state and side effects efficiently.

ASP.NET Core is a cross-platform, high-performance framework for building modern, cloud-based, internet-connected applications.

• Cross-platform framework for building web applications

• High-performance and scalable

• Supports cloud-based and internet-connected applications

• Open-source and actively maintained by Microsoft

• Modular design for flexibility and extensibility

Key features of ASP Dot Net CORE include cross-platform support, high performance, and modularity.

• Cross-platform support allows developers to build and run applications on Windows, macOS, and Linux.

• High performance achieved through features like a new lightweight and modular HTTP request pipeline.

• Modularity enables developers to include only the necessary components in their applications, reducing the overall size and ...read more

Entity Framework Core is an ORM framework that allows developers to work with databases using .NET applications.

• Entity Framework Core is an Object-Relational Mapping (ORM) framework for .NET applications.

• It allows developers to work with databases using .NET objects and LINQ queries.

• EF Core supports various database providers such as SQL Server, SQLite, MySQL, etc.

• It simplifies data access and persistence by handling d...read more

Use the DISTINCT keyword in an SQL query to remove duplicate records.

• Use the SELECT DISTINCT statement to retrieve unique records.

• Identify the columns that should be used to determine uniqueness.

• Consider using GROUP BY clause with aggregate functions if needed.

Joins are used to combine rows from two or more tables based on a related column, while subqueries are nested queries used to return data for the main query.

• Joins are used to retrieve data from multiple tables based on a related column

• Subqueries are nested queries within a main query to return data for the main query

• Joins are typically more efficient than subqueries for large datasets

• Joins can be of different types lik...read more

Views are virtual tables, procedures are reusable code blocks, functions return values

• Views are virtual tables that display data from one or more tables

• Procedures are reusable code blocks that can be called multiple times

• Functions return a single value based on input parameters

• Views are read-only, while procedures and functions can modify data

• Examples: View - SELECT * FROM employees_view; Procedure - EXECUTE get_employ...read more

Code First: Develop database from code. Database First: Generate code from existing database.

• Code First: Focus on code design and then generate database schema.

• Database First: Focus on existing database schema and generate code classes.

• Code First: More control over database design and relationships.

• Database First: Faster development for existing databases.

• Code First: Entity Framework Code First approach.

• Database First:...read more

To connect SQL to ASP Core Web API, you need to configure a database connection in the API project.

• Configure a connection string in the appsettings.json file of the API project.

• Install Entity Framework Core package in the API project.

• Create a DbContext class that inherits from DbContext and represents the database.

• Use dependency injection to inject the DbContext into the API controllers.

Dependency Injection is a design pattern where the dependencies of an object are provided externally rather than created within the object itself.

• Dependencies are injected into a class through constructor injection, setter injection, or interface injection.

• This helps in achieving loose coupling between classes and makes the code more testable and maintainable.

• Example: Instead of creating an instance of a dependency wit...read more

LINQ (Language Integrated Query) is a feature in C# that allows for querying data from different data sources using a uniform syntax.

• LINQ allows for querying data from collections, databases, XML, and more.

• It provides a set of standard query operators like Where, Select, OrderBy, etc.

• LINQ queries are written in a declarative syntax similar to SQL.

• Example: var result = from num in numbers where num % 2 == 0 select num;

Enable JWT Authentication in ASP Core Web API with Roles

• Install the required NuGet packages like Microsoft.AspNetCore.Authentication.JwtBearer

• Configure JWT authentication in Startup.cs file

• Add authentication middleware in Configure method

• Implement role-based authorization using policies and attributes

Optimizing SQL queries involves using indexes, minimizing data retrieval, and avoiding unnecessary joins.

• Use indexes on columns frequently used in WHERE clauses

• Minimize data retrieval by selecting only necessary columns

• Avoid unnecessary joins by using EXISTS or IN clauses instead of JOINs

Use indexing, limit the columns retrieved, optimize queries, use pagination

• Create indexes on columns frequently used in queries

• Limit the columns retrieved to only those needed

• Optimize queries by using WHERE clauses and avoiding SELECT *

• Implement pagination to retrieve records in smaller chunks

Indexing in SQL is used to improve the performance of queries by creating a data structure that allows for faster retrieval of data.

• Types of indexing include clustered and non-clustered indexes

• Clustered indexes physically order the data in the table based on the index key

• Non-clustered indexes create a separate data structure that includes the indexed columns and a pointer to the actual data

• Indexes can be created on sin...read more

I have 3 years of experience as an ASP Core Web API and ReactJs Developer.

• 3 years of experience in ASP Core Web API development

• Proficient in ReactJs development

• Developed multiple projects using ASP Core Web API and ReactJs

States are mutable data managed within a component, while Props are immutable data passed from parent to child components.

• States are managed within a component and can be changed by the component itself

• Props are passed from parent to child components and cannot be changed by the child component

• States are used for internal component data management, while Props are used for passing data from parent to child components

Context API is a built-in feature in React for managing global state, while Redux is a standalone library for state management.

• Context API is built into React, while Redux is a separate library.

• Context API is primarily used for managing global state in a React application.

• Redux provides a centralized store for managing state across the application.

• Context API is simpler to use for smaller applications, while Redux is m...read more