安卓sql数据库源代码

public class MyDatabaseHelper extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 2;
    private static final String DATABASE_NAME = "mydatabase.db";

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

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (oldVersion < 2) {
            // 执行数据库升级操作
            db.execSQL("ALTER TABLE mytable ADD COLUMN newcolumn TEXT");
        }
    }
}

String sql = "SELECT * FROM mytable WHERE id = ?";
Cursor cursor = db.rawQuery(sql, new String[]{id});

public class MainActivity extends AppCompatActivity {
    private MyDatabaseHelper dbHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dbHelper = new MyDatabaseHelper(this);
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        // 插入数据
        ContentValues values = new ContentValues();
        values.put("name", "John");
        db.insert("mytable", null, values);

        // 查询数据
        Cursor cursor = db.query("mytable", null, null, null, null, null, null);
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndex("name"));
            Log.d("MainActivity", "Name: " + name);
        }
        cursor.close();
    }

    @Override
    protected void onDestroy() {
        dbHelper.close();
        super.onDestroy();
    }
}