Entity, DAO, Database classes in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an <strong>Entity</strong> class in Android Room?

An Entity class represents a table in the database. Each instance of the class is a row in that table. It uses annotations like @Entity and @PrimaryKey to define the table and its primary key.

beginner

What does a DAO (Data Access Object) do in Room?

A DAO defines methods to access the database, like inserting, updating, deleting, and querying data. It uses annotations like @Insert, @Update, @Delete, and @Query to specify SQL operations.

beginner

What is the role of the <strong>Database</strong> class in Room?

The Database class holds the database and serves as the main access point. It is an abstract class annotated with @Database and lists the entities and version. It provides abstract methods to get DAOs.

intermediate

Why do we use annotations like @Entity, @Dao, and @Database in Room?

Annotations tell Room how to generate the necessary code. @Entity marks a data class as a table, @Dao marks an interface or abstract class for database operations, and @Database defines the database configuration.

intermediate

How does Room help with database operations compared to raw SQLite?

Room provides a simple, type-safe way to work with SQLite databases. It reduces boilerplate code, handles SQL queries with annotations, and integrates with Kotlin coroutines and LiveData for reactive apps.

Which annotation marks a Kotlin data class as a database table in Room?

A @Entity

B @Dao

C @Database

D @Table

The @Entity annotation marks a class as a table in Room.

What does the @Dao annotation indicate?

A Defines a database table

B Defines a primary key

C Defines the database version

D Defines database access methods

The @Dao annotation marks an interface or abstract class that contains methods to access the database.

Which class holds the database and provides DAOs in Room?

A Entity class

B Database class

C DAO class

D Repository class

The Database class is the main access point to the database and provides DAOs.

Which annotation specifies the database version in Room?

A @Entity(version = 1)

B @Dao(version = 1)

C @Database(version = 1)

D @Version(1)

The @Database annotation includes the version number of the database.

What is the purpose of the @PrimaryKey annotation in an Entity?

A Marks a field as the unique identifier

B Marks a method as primary

C Marks a class as primary

D Marks a query as primary

The @PrimaryKey annotation marks a field as the unique identifier for each row in the table.

Explain the roles of Entity, DAO, and Database classes in Android Room.

Think about how data is stored, accessed, and managed.

Describe how annotations help Room generate database code.

Annotations are like labels telling Room what to do.