Pharmed Interview Questions and Answers

Command Class is a class in .NET that represents a command to be executed.

• Command Class is used to encapsulate a command to be executed, along with any parameters or options.

• It helps in separating the command logic from the rest of the application.

• Examples include SqlCommand in ADO.NET for executing SQL commands and ProcessStartInfo in System.Diagnostics for starting external processes.

Constraints are rules defined on a column to enforce data integrity and consistency in a database.

• Constraints ensure that data in a database meets certain criteria.

• Common types of constraints include NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, and CHECK constraints.

• For example, a NOT NULL constraint ensures that a column cannot have a NULL value, while a UNIQUE constraint ensures that all values in a column are unique.

ViewState is a client-side state management technique used in ASP.NET to store page-specific data.

• ViewState is used to persist data between postbacks on a web page.

• It stores data in a hidden field on the page which is sent to the client and back to the server.

• ViewState is specific to a single page and is not shared between pages.

• It can be used to store simple data types like strings or complex objects.

• Example: ViewState['username'] = 'JohnDoe';

Cookies are small pieces of data stored on the client's computer by the web server to track user activity and preferences.

• Cookies are used to store user preferences, login information, shopping cart items, etc.

• They can be set by the server using the Set-Cookie header in HTTP response.

• Cookies can be accessed and modified by the client-side scripts like JavaScript.

• They have an expiration date and can be either session cookies (deleted when the browser is closed) or persistent c...read more

Cache is a hardware or software component that stores data so that future requests for that data can be served faster.

• Cache helps in improving the performance of applications by reducing the time taken to fetch data from the main memory or disk.

• Examples of cache include browser cache, CPU cache, and database cache.

• Cache can be implemented at different levels such as client-side cache, server-side cache, and distributed cache.

A subquery is a query nested within another query, used to return data that will be used in the main query.

• Subqueries can be used in SELECT, INSERT, UPDATE, and DELETE statements.

• They can be used to retrieve data from one table based on values from another table.

• Subqueries can be correlated or non-correlated, depending on whether they reference columns from the outer query.

• Example: SELECT * FROM table1 WHERE column1 = (SELECT column2 FROM table2 WHERE condition);