Database migrations in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Room database version.

Android Kotlin

val db = Room.databaseBuilder(context, AppDatabase::class.java, "app_db")
  .version([1])
  .build()

Drag options to blanks, or click blank then click option'

A2

B1

C3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using version 0 which is invalid

Skipping version number

The initial version of a Room database is usually set to 1.

2fill in blank

medium

Complete the code to add a migration from version 1 to 2.

Android Kotlin

val MIGRATION_1_2 = object : Migration(1, 2) {
  override fun migrate(database: SupportSQLiteDatabase) {
    database.execSQL([1])
  }
}

Drag options to blanks, or click blank then click option'

A"ALTER TABLE users ADD COLUMN age INTEGER DEFAULT 0"

B"DROP TABLE users"

C"CREATE TABLE users"

D"SELECT * FROM users"

Attempts:

3 left

💡 Hint

Common Mistakes

Dropping tables accidentally

Using SELECT instead of ALTER

To migrate from version 1 to 2, we add a new column 'age' with a default value.

3fill in blank

hard

Fix the error in the migration code to rename a table.

Android Kotlin

val MIGRATION_2_3 = object : Migration(2, 3) {
  override fun migrate(database: SupportSQLiteDatabase) {
    database.execSQL("ALTER TABLE users RENAME TO [1]")
  }
}

Drag options to blanks, or click blank then click option'

Ausers

Busers_new

Cusers_old

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name as original

Using invalid table names

To rename the table 'users' to 'users_old', the new name must be specified correctly.

4fill in blank

hard

Fill both blanks to create a migration that creates a new table.

Android Kotlin

val MIGRATION_3_4 = object : Migration(3, 4) {
  override fun migrate(database: SupportSQLiteDatabase) {
    database.execSQL("CREATE TABLE [1] (id INTEGER PRIMARY KEY, name TEXT)")
    database.execSQL("INSERT INTO [2] (id, name) VALUES (1, 'Alice')")
  }
}

Drag options to blanks, or click blank then click option'

Aemployees

Busers

Ccustomers

Dstaff

Attempts:

3 left

💡 Hint

Common Mistakes

Using different table names in CREATE and INSERT

Using reserved keywords as table names

Both blanks must use the same table name 'employees' to create and insert data correctly.

5fill in blank

hard

Fill all three blanks to define a migration that adds a new column and updates data.

Android Kotlin

val MIGRATION_4_5 = object : Migration(4, 5) {
  override fun migrate(database: SupportSQLiteDatabase) {
    database.execSQL("ALTER TABLE [1] ADD COLUMN [2] INTEGER DEFAULT 0")
    database.execSQL("UPDATE [3] SET [2] = 10 WHERE id = 1")
  }
}

Drag options to blanks, or click blank then click option'

Ausers

Bage

Dscore

Attempts:

3 left

💡 Hint

Common Mistakes

Using different table names in ALTER and UPDATE

Using invalid column names

The migration adds a new column 'score' to the 'users' table and updates it for a specific row.