Database and Data Access

Question 1

What is ADO.NET?

Answer 1

ADO.NET is a data access technology in .NET that provides a set of classes for connecting to databases, executing queries, and managing data.

Question 2

How does ADO.NET manage data access?

Answer 2

ADO.NET uses data providers to connect to various types of data sources. The core data providers are SqlConnection for SQL Server, OleDbConnection for OLE DB, and OracleConnection for Oracle.

Question 3

Explain the difference between DataSet and DataReader in ADO.NET.

Answer 3

DataSet is an in-memory representation of data that supports relational data, relationships, and multiple tables. DataReader is a forward-only, read-only stream of data that’s more memory-efficient for reading large datasets.

Question 4

What is Entity Framework (EF)?

Answer 4

Entity Framework is an Object-Relational Mapping (ORM) framework that simplifies database access by allowing you to work with database entities as if they were regular .NET objects.

Question 5

What are the different approaches for working with EF?

Answer 5

EF supports two approaches: Database-First (where the database schema is generated from the existing database) and Code-First (where the database schema is generated from your C# classes).

Question 6

What is a SQL JOIN?

Answer 6

A SQL JOIN combines rows from two or more tables based on a related column between them. Common types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

Question 7

Explain stored procedures in the context of databases.

Answer 7

A stored procedure is a precompiled set of one or more SQL statements that can be executed by calling the procedure’s name. They offer reusability, security, and performance benefits.

Question 8

What is an ORM?

Answer 8

ORM stands for Object-Relational Mapping. It’s a technique for mapping database tables and relationships to programming language objects, making database interactions more object-oriented.

Question 9

How does Entity Framework handle lazy loading?

Answer 9

Lazy loading is a technique where related entities are loaded from the database only when accessed for the first time. EF supports lazy loading through proxy objects.

Question 10

What is the purpose of the DbContext class in Entity Framework?

Answer 10

The DbContext class is the main entry point to the Entity Framework. It represents the session with the database and provides methods to query, insert, update, and delete data.

Question 11

What is the Entity Framework Core (EF Core)?

Answer 11

EF Core is a lightweight and cross-platform version of Entity Framework, designed for building applications that run on .NET Core and .NET 5+.

Question 12

How does Entity Framework Core differ from Entity Framework (EF)?

Answer 12

EF Core is a reimagined and modernized version of EF, with improved performance, support for different platforms, and a simplified API. It’s optimized for microservices and cloud-based applications.

Question 13

What are migrations in Entity Framework?

Answer 13

Migrations are a way to manage database schema changes over time. They allow you to apply changes to the database schema as your model evolves.

Question 14

What is LINQ to SQL?

Answer 14

LINQ to SQL is a component of ADO.NET that allows you to use LINQ (Language Integrated Query) syntax to query and manipulate SQL Server databases.

Question 15

Explain the concept of database normalization.

Answer 15

Database normalization is the process of organizing a database’s schema to reduce data redundancy and improve data integrity. It involves breaking down tables into smaller, related tables.

Question 16

How can you prevent SQL injection when executing raw SQL queries in ADO.NET or Entity Framework?

Answer 16

To prevent SQL injection, use parameterized queries. Parameters ensure that user input is treated as values and not executable code.

Question 17

What is the purpose of an Object-Relational Mapping (ORM) tool like Entity Framework?

Answer 17

An ORM simplifies the process of interacting with databases by abstracting the details of SQL queries and providing a higher-level, object-oriented interface for database operations.

Question 18

How can you optimize database performance in Entity Framework applications?

Answer 18

Optimize performance by minimizing the number of database queries, using appropriate indexes, avoiding the N+1 query problem, and using appropriate caching strategies.

Question 19

Explain the concept of a database transaction.

Answer 19

A database transaction is a sequence of one or more SQL statements executed as a single unit of work. It ensures data integrity by either committing all changes or rolling them back if an error occurs.

Question 20

What is the difference between an INNER JOIN and a LEFT JOIN?

Answer 20

An INNER JOIN returns only the matching rows from both tables based on the specified condition. A LEFT JOIN returns all rows from the left table and matching rows from the right table, filling in with NULLs where no match is found.

Question 21

Explain the purpose of a foreign key in a database.

Answer 21

A foreign key establishes a link between two tables by referencing the primary key of another table. It enforces referential integrity and maintains relationships between data.

Question 22

What are the advantages of using stored procedures over inline SQL queries?

Answer 22

Stored procedures provide encapsulation, security, and performance benefits. They can be precompiled, cached, and centrally managed.

Question 23

Describe the ACID properties of a database transaction.

Answer 23

ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties ensure that transactions are reliable, consistent, and maintain data integrity.

Question 24

What is lazy loading in Entity Framework?

Answer 24

Lazy loading is a feature in EF that delays the loading of related entities until they are explicitly accessed. This can help improve performance by reducing unnecessary data retrieval.

Question 24

Explain the concept of connection pooling.

Answer 24

Connection pooling involves reusing database connections to reduce the overhead of opening and closing connections. It enhances the performance of database interactions.

Question 24

How can you improve Entity Framework performance when dealing with a large number of entities?

Answer 24

Use paging techniques to limit the number of retrieved records, implement proper indexing, utilize caching mechanisms, and consider asynchronous programming for responsiveness.

Question 24

What is the role of a DataAdapter in ADO.NET?

Answer 24

A DataAdapter acts as a bridge between a dataset and a data source. It facilitates data retrieval and manipulation between the dataset and the database.

Question 25

Explain the concept of code-first migrations in Entity Framework.

Answer 25

Code-first migrations allow you to create and update the database schema based on changes to your C# classes. Migrations are generated based on the differences between the model and the existing schema.

Question 26

What is a self-referencing table in a database?

Answer 26

A self-referencing table is a table that has a foreign key column referencing its own primary key column. This can be used to represent hierarchical or recursive relationships.

Question 27

What is database indexing, and why is it important?

Answer 27

Database indexing is a technique that improves data retrieval speed by creating optimized data structures. Indexes allow the database system to quickly locate rows based on specific column values.

Question 28

What is the Entity Framework Database First approach?

Answer 28

The Database First approach involves generating C# classes and a model based on an existing database schema. It’s suitable when working with an existing database that you want to integrate into your application.

Question 29

How does Entity Framework handle database relationships and navigation properties?

Answer 29

EF uses navigation properties to define relationships between entities. These properties allow you to navigate from one entity to another without writing explicit SQL queries.

Question 30

What is the purpose of a connection string in ADO.NET or Entity Framework?

Answer 30

A connection string contains information needed to connect to a database. It includes details like the database server’s address, credentials, and database name.

Question 31

What is SQL Injection, and how can you prevent it?

Answer 31

SQL Injection is a security vulnerability where malicious SQL code is injected into input fields. Prevent it by using parameterized queries or prepared statements to sanitize user input.

Question 32

Explain the concept of LINQ (Language Integrated Query).

Answer 32

LINQ is a feature in C# that allows you to write queries against collections, databases, XML, and more using a consistent syntax. It brings query capabilities directly into the language.

Question 33

What is normalization, and how does it relate to database design?

Answer 33

Normalization is the process of organizing data in a database to minimize redundancy and dependency issues. It helps maintain data integrity and reduces anomalies.

Question 34

How can you ensure data consistency when dealing with multiple related tables in a database?

Answer 34

Use transactions to group related operations into a single unit of work. Transactions ensure that either all changes are applied or none of them are, maintaining data integrity.

Question 35

Explain the concept of database denormalization and when it might be used.

Answer 35

Denormalization involves intentionally introducing redundancy into a database design for performance optimization. It’s used when read performance is more critical than data modification efficiency.

Question 36

What are views in a database, and why are they used?

Answer 36

Views are virtual tables created by defining a SELECT statement. They simplify complex queries, abstract underlying table structures, and offer an additional security layer.

Question 37

What are the benefits of using an ORM like Entity Framework over writing raw SQL queries?

Answer 37

ORMs abstract away low-level database interactions, making code more readable and maintainable. They also provide a higher level of abstraction and support for various database systems.

Question 38

What is an identity column in a database table?

Answer 38

An identity column is a column that automatically generates unique values for each new row added to a table. It’s commonly used as a primary key.

Question 39

What is the role of the DatabaseContext in Entity Framework Code-First?

Answer 39

The DbContext class is the main entry point to the Entity Framework when using the Code-First approach. It represents the session with the database and manages interactions with it.

Question 40

Explain the concept of database indexes and their types.

Answer 40

Indexes are data structures that improve data retrieval efficiency. Types include clustered (determines the physical order of data) and non-clustered (additional data structure).

Question 41

What are stored procedures and how can they enhance database performance?

Answer 41

Stored procedures are precompiled sets of SQL statements that can be executed with a single call. They can reduce network traffic and improve security by centralizing data access logic.

Question 42

How can you handle database concurrency issues when multiple users are modifying the same data simultaneously?

Answer 42

Techniques include optimistic concurrency (using version numbers or timestamps) and pessimistic concurrency (using locks) to prevent conflicting changes.

Question 43

Explain the concept of LINQ to Entities in Entity Framework.

Answer 43

LINQ to Entities allows you to use LINQ queries to retrieve data from a database through EF. The LINQ query is translated into SQL and executed on the database.

Question 44

What is the purpose of the Database class in Entity Framework?

Answer 44

The Database class in EF provides methods for working directly with the database, such as creating, deleting, and checking for its existence

Question 45

What are transactions in database operations, and why are they important?

Answer 45

Transactions ensure the atomicity and consistency of multiple related database operations. They either complete all changes or roll them back if an error occurs.

Question 46

Explain the difference between a primary key and a unique key in a database.

Answer 46

A primary key uniquely identifies a row in a table and ensures data integrity. A unique key enforces uniqueness but doesn’t necessarily serve as the primary identifier for a row.

Question 47

Explain the concept of database connection pooling and its benefits.

Answer 47

Database connection pooling is a technique where a pool of database connections is maintained and reused to minimize the overhead of opening and closing connections. This improves application performance by reducing the time required to establish a new connection each time.