DXC Technology Interview Questions and Answers

Joins are generally faster than subqueries.

• Joins are typically faster than subqueries because they allow the database to retrieve data in a more efficient manner.

• Subqueries can be slower because they are executed for each row of the outer query, leading to potential performance issues.

• However, the performance can vary depending on the specific query and database optimization.

• In general, it is recommended to use joins over subqueries for better performance.

Token is a unique identifier used for authentication, while refresh token is used to obtain a new access token.

• Token is a unique string that is used to authenticate a user or device.

• Refresh token is used to obtain a new access token after the original token expires.

• Tokens are commonly used in OAuth authentication.

• Example: Access token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9. Refresh token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.

Status codes in API are standardized codes returned by a server in response to a client's request.

• Status codes indicate the outcome of the request (e.g. success, error, redirection)

• Common status codes include 200 (OK), 404 (Not Found), 500 (Internal Server Error)

• Status codes are grouped into different categories (e.g. 2xx for success, 4xx for client errors, 5xx for server errors)

DI in dotnet core stands for Dependency Injection, a design pattern used to achieve loose coupling between components.

• DI allows for injecting dependencies into a class rather than creating them within the class itself.

• It helps in achieving separation of concerns and makes the code more testable and maintainable.

• Example: In dotnet core, services can be registered in the Startup class and injected into controllers or other classes.

Isolation in SQL refers to the ability to control the visibility of changes made by one transaction to other transactions.

• Isolation levels in SQL determine how transactions interact with each other

• Higher isolation levels provide more control over visibility of changes

• Common isolation levels include READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, and SERIALIZABLE