android sqliteopenhelper

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "mydatabase.db";
    private static final int DATABASE_VERSION = 1;

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建数据表
        db.execSQL("CREATE TABLE mytable (_id INTEGER PRIMARY KEY, name TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 升级数据库时的操作，例如删除旧表并重新创建
        db.execSQL("DROP TABLE IF EXISTS mytable");
        onCreate(db);
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    switch (oldVersion) {
        case 1:
            // 执行从版本1到版本2的升级操作
            db.execSQL("ALTER TABLE mytable ADD COLUMN new_column TEXT");
        case 2:
            // 执行从版本2到版本3的升级操作
            // ...
    }
}