Hello Dev, Here is the list of the most frequently asked questions of Room Database in interviews with answers.
1:- What is Room in Android, and why is it used?
Room is a persistence library that provides an abstraction layer over SQLite for local data storage in Android applications. It simplifies database interactions by offering an efficient way to work with databases.
2:- What are the core components of Room, and what is their purpose?
Room consists of three main components: Entity, DAO (Data Access Object), and Database. Entities define the structure of the database tables, DAOs provide methods for database operations, and the Database class ties everything together.
3:- Explain the purpose of the @Entity annotation in Room.
The @Entity annotation is used to define a class as an entity, which represents a table in the database. It specifies the table name and can include fields, primary keys, and other properties of the table.
4:- What is a DAO in Room, and how does it simplify database operations?
A DAO (Data Access Object) in Room is an interface or abstract class that defines methods for performing database operations, such as insert, update, delete, and query. It simplifies database interactions by providing a clean API.
5:- How do you define relationships between entities in Room?
You can define relationships between entities in Room using annotations like @ForeignKey, @Relation, and @Embedded. These annotations help establish associations between tables/entities.
6:- What is the purpose of the @Database annotation in Room, and how is it used?
The @Database annotation is used to define a database class that acts as the main entry point to access the database. It specifies the list of entities and the database version. Room automatically generates the implementation for this class.
7:- Explain the difference between @PrimaryKey and @ColumnInfo annotations in Room.
@PrimaryKey is used to designate a field as the primary key of an entity, ensuring each record has a unique identifier. @ColumnInfo allows you to specify details about a column, such as its name and whether it’s nullable.
8:- How does Room handle database migrations, and what is the purpose of the @Migration annotation?
Room provides automatic database schema migrations when you update the database version. The @Migration annotation is used to define migration steps to preserve existing data when the schema changes.
9:- What is the purpose of LiveData integration with Room, and how does it benefit Android app development?
LiveData integration with Room allows for real-time updates of UI components when data in the database changes. It simplifies the handling of database updates, ensuring that UI always reflects the most current data.
10:- How can you perform complex queries with Room that involve multiple tables/entities?
You can use SQL queries or methods in the DAO to perform complex queries involving multiple tables/entities. Room allows you to write custom SQL queries when needed.
11:- Explain the differences between Room and other local database solutions like SQLiteOpenHelper.
Room is an abstraction layer over SQLite that provides compile-time checks, simplified database operations, and automatic query generation. SQLiteOpenHelper requires more manual database management and SQL query writing.
12:- What is the role of the @TypeConverter annotation in Room, and when is it used?
The @TypeConverter annotation is used to define custom type converters for non-supported data types in Room. It allows you to specify how Room should convert between custom types and database columns.
13:- How do you handle database operations on a background thread with Room to avoid blocking the main (UI) thread?
You can use asynchronous methods in the DAO or use Kotlin Coroutines or RxJava to perform database operations on background threads, ensuring that the UI thread remains responsive.
14:- What are some best practices for optimizing database performance when using Room in Android apps?
Best practices include using appropriate indexes, optimizing queries, batching operations, and using background threads for database operations. Additionally, keeping the database schema simple and efficient is essential.
15:- How do you handle data migration when changing the schema of a Room database?
Room provides mechanisms for handling data migration using the @Migration annotation. You define migration steps to transform the old schema to the new schema while preserving existing data.
16:- Can you use Room with other Android architecture components like LiveData and ViewModel? If so, how do they work together?
Yes, Room works seamlessly with LiveData and ViewModel. LiveData can be used to observe changes in Room database data, and ViewModel can retain data across configuration changes, providing a convenient way to manage UI-related data.
17:- Explain how you can ensure data integrity and consistency when using Room in a multi-threaded environment.
You can use transactions in Room to ensure data integrity and consistency when multiple threads are performing database operations. Transactions help maintain the atomicity of operations, ensuring that the database remains in a consistent state.
18:- What are the advantages of using Room over raw SQLite in Android app development?
Room provides a higher-level abstraction, compile-time checks, easier schema management, and integration with other Android architecture components, making it a more developer-friendly choice compared to raw SQLite.
19:- Can you use Room for working with remote data sources, such as web APIs, in addition to local databases?
While Room is primarily designed for local databases, you can use it in combination with other libraries, such as Retrofit or OkHttp, to cache and manage remote data locally.
20:- How can you write unit tests for Room database operations to ensure their correctness?
You can write unit tests for Room database operations using in-memory databases or instrumented tests with a test database. Room provides testing support to verify that your database operations work as expected.
21:- Romm V/S SQLite
- It checks the query at compile time.
- It is easy in-room data migration.
- It maps database objects to Java objects very easily and with very little boilerplate code.
- It can work with live data.
- There is no compile time check of the SQL query.
- Updating database schema is very difficult.
- Converting SQL queries to Java objects is difficult and requires too much boilerplate code.
- It can not work with live data.