Write the use of onCreate( ), onUpgrade ( ) and getWritable Database( ) methods. With exampl

The methods onCreate(), onUpgrade(), and getWritableDatabase() are important components of SQLite database management in Android development. Here's a detailed explanation of each method:

1. onCreate()

• Purpose: This method is called when the database is created for the first time. It is where you initialize the database schema.
• Usage: You define the SQL commands to create tables and initialize data.
• Example:

  @Override
  public void onCreate(SQLiteDatabase db) {
      String CREATE_TABLE = "CREATE TABLE Users (id INTEGER PRIMARY KEY, name TEXT, email TEXT)";
      db.execSQL(CREATE_TABLE);
  }
  

2. onUpgrade()

• Purpose: This method is called when the database needs to be upgraded (i.e., when the database version number is increased).
• Usage: You implement the logic to handle schema changes, such as altering tables or migrating data.
• Example:

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      db.execSQL("DROP TABLE IF EXISTS Users");
      onCreate(db);  // Recreate the database
  }
  

3. getWritableDatabase()

• Purpose: This method returns a writable instance of the database. If the database exists and is writable, it opens it; otherwise, it creates a new one.
• Usage: You call this method when you need to write data to the database, such as inserting or updating records.
• Example:

  SQLiteDatabase db = this.getWritableDatabase();
  ContentValues values = new ContentValues();
  values.put("name", "John Doe");
  values.put("email", "[email protected]");
  db.insert("Users", null, values);
  

Summary

In summary, onCreate() is crucial for setting up the initial database structure, onUpgrade() manages schema changes for different database versions, and getWritableDatabase() provides means for handling database write operations. Proper implementation of these methods is essential for effective database management in Android applications.