SQLITE Cursor不显示空值

Question

是否有任何文档说SQLITE Cursor不会显示空值？如您所见，LOGCAT也没有显示空值。

如果是这样，如何为空字段获取空字符串（“”）？我无法用空字段填充我的JSON。例如，在下面的例子中，我想在每个JSON对象中有4个元素，但我只得到2个。

CODE：

String selectQuery = "SELECT  * FROM " + TABLE_NAME + " WHERE "+KEY_ID+" = 73";
SQLiteDatabase db = this.getReadableDatabase();
Cursor row = db.rawQuery(selectQuery, null);
if (row.moveToFirst()) {
    JSONObject prebook;
    do {
        Log.d("a1",""+row.getString(3)); //THIS FIELD IS EMPTY
        Log.d("a2",""+row.getString(2));  //THIS FIELD IS EMPTY
        Log.d("a3",""+row.getString(1)); //THIS FIELD HAS A VALUE
        prebook = new JSONObject();
        prebook.put(KEY_ID, row.getString(0));
        prebook.put(KEY_NAME, row.getString(1));
        prebook.put(KEY_PRINT_NAME, row.getString(2)); // THIS ELEMENT NEVER ADDED INTO THE JSON
        prebook.put(KEY_GENRE, row.getString(3)); // THIS ELEMENT NEVER ADDED INTO THE JSON
    } while (row.moveToNext());
}

logcat的：

12-07 12:43:21.480: D/a3(2283): Farmer Boy