Scenario: You are developing an application that needs to connect to a PostgreSQL database. Which ADO.NET data provider would be suitable for this task?
- Npgsql
- OleDb
- OracleClient
- SqlClient
Npgsql is the ADO.NET data provider specifically designed for PostgreSQL databases. It offers efficient connectivity and optimized performance when working with PostgreSQL. Using Npgsql ensures seamless integration between your application and the PostgreSQL database, enabling reliable data access and manipulation.
What is the primary purpose of a data reader in ADO.NET?
- To establish a connection to the database
- To execute stored procedures
- To read and process data from a data source sequentially
- To update data in the database
A data reader in ADO.NET is primarily used to sequentially read and process data from a data source. It provides a forward-only, read-only stream of data from a database, allowing efficient retrieval of large datasets without storing the entire result set in memory. This makes it suitable for scenarios where fast, lightweight data access is required, such as data retrieval operations in web applications or data processing tasks.
The SelectCommand property of a DataAdapter specifies the ___________ that will be executed to retrieve data.
- SQL query
- Stored procedure
- Table name
- View name
The SelectCommand property of a DataAdapter specifies the SQL query that will be executed to retrieve data from the database. This query is typically a SELECT statement that fetches the desired data from one or more tables.
Scenario: In Entity Framework, you need to update a record only if it meets certain conditions. How can you achieve this while updating data in EF?
- Fetch all records and filter them programmatically in C# code before updating the necessary record.
- Manually check conditions in C# code after retrieving the record and before updating it.
- Update all records and then revert changes for records that do not meet the specified conditions.
- Use the Where method in LINQ query to filter records based on conditions before updating.
In Entity Framework, to update a record only if it meets certain conditions, you can use the Where method in LINQ query to filter records based on conditions before performing the update operation. This ensures that only the records meeting the specified criteria are updated, minimizing unnecessary database operations. Fetching all records and filtering them programmatically or updating all records and then reverting changes are inefficient and prone to errors. Manually checking conditions in C# code introduces unnecessary complexity and reduces maintainability.
How does LINQ to Entities handle complex queries involving multiple tables and relationships?
- Relies on stored procedures for complex queries.
- Requires explicit JOIN clauses in LINQ queries.
- Uses automatic query optimization based on the entity model structure.
- Utilizes LINQ queries to generate SQL statements for optimized database access.
LINQ to Entities leverages its query provider to translate LINQ queries into SQL statements, optimizing them for database access and efficiently handling complex joins and relationships within the entity model.
The ExecuteNonQuery method returns the number of ___________ affected by the non-query command.
- Columns
- Databases
- Rows
- Tables
In ADO.NET, the ExecuteNonQuery method is typically used for non-query commands such as INSERT, UPDATE, DELETE, etc. It returns the number of rows affected by the execution of the command.
When mapping entities to database tables, the ___________ attribute can be used to specify column names that differ from property names.
- [Column]
- [ForeignKey]
- [PrimaryKey]
- [Table]
When mapping entities to database tables, the "[Column]" attribute can be used to specify column names that differ from property names. This is particularly useful when you have properties with names that don't match your database column names. By using [Column], you can explicitly specify the column name that should be mapped to the property.
When working with multiple tables in a SELECT statement, what SQL clause is used to specify how the tables are related?
- GROUP BY
- HAVING
- JOIN
- WHERE
The JOIN clause is used in SQL to combine rows from two or more tables based on a related column between them. It allows you to retrieve data from multiple tables in a single query by specifying how the tables are related. There are different types of JOINs, such as INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN, each serving different purposes in querying data from related tables.
To update data in Entity Framework, you typically modify the properties of an ___________.
- DbContext
- Entity Object
- SQL Query
- Stored Procedure
In Entity Framework, you update data by modifying the properties of an Entity Object, which represents a database record. This allows for object-oriented manipulation of data.
Scenario: Your application is experiencing a high volume of database requests. How can you optimize the connection management to handle this load efficiently?
- Connection Pooling
- Increase Connection Timeout
- Disable Connection Pooling
- Increase Max Pool Size
Option 1, "Connection Pooling," is the correct choice. Implementing connection pooling allows your application to reuse existing connections rather than creating new ones for each request. This helps in efficiently managing resources and improving performance, especially in scenarios with a high volume of database requests. By keeping a pool of established connections, the overhead of creating and tearing down connections is minimized, resulting in better scalability and responsiveness of the application.