Question

我有一个方法应该升级给定用户的unreadMessageCount。

public void increaseUnreadMessageCount(int userID) {
    String query = "UPDATE " + tableName + " SET " + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " = "
            + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " + 1 WHERE " + DatabaseHelper.KEY_USER_USER_ID
            + " = ?";
    Log.i("query", query);
    db.rawQuery(query, new String[] { String.valueOf(userID) });
}

这评估为：UPDATE user SET unreadPrivateMessageCount = unreadPrivateMessageCount + 1 WHERE userID = ?这对我来说是正确的。但不知何故它不起作用，行总是0。

或者我的SELECT语句错了吗？

public int getUnreadPrivateMessageCount() {
    String query = "SELECT SUM(" + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + ") AS messageCount FROM "
            + tableName + " WHERE " + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " <> ?";
    Log.i("query", query);
    Cursor cursor = db.rawQuery(query, new String[] { "0" });
    int messageCount = 0;
    if (cursor.getCount() > 0) {
        if (cursor.moveToFirst()) {
            messageCount = cursor.getInt(cursor.getColumnIndexOrThrow("messageCount"));
            cursor.close();
        } else {
            Log.e("getUnreadPrivateMessageCount", "moveToFirst failed");
        }

    } else {
        Log.e("getUnreadPrivateMessageCount", "count 0");
    }

    return messageCount;
}

此查询的计算结果为SELECT SUM(unreadPrivateMessageCount) AS messageCount FROM user WHERE unreadPrivateMessageCount <> ?，并且未触发任何错误日志，这对我来说也是正确的。

Answer 1

rawQuery用于执行查询，即SELECT语句。要执行其他SQL语句，请改用execSQL。

另外，请检查您是否确实要将ID视为字符串。

Answer 2

如果您的更新语法正确，则：

public void increaseUnreadMessageCount(int userID) {
    String query = "UPDATE " + tableName + " SET " + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " = "
            + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " + 1 WHERE " + DatabaseHelper.KEY_USER_USER_ID
            + " = ?";
    Log.i("query", query);
    db.rawQuery(query, new String[] { String.valueOf(userID) });
}

你在哪里使用：getUnreadPrivateMessageCount()，没有，所以它必须是这样的：

public void increaseUnreadMessageCount(int userID) {
    String query = "UPDATE " + tableName + " SET " + DatabaseHelper.KEY_USER_UNREAD_MESSAGE_COUNT + " = "
            + getUnreadPrivateMessageCount() + " WHERE " + DatabaseHelper.KEY_USER_USER_ID
            + " = ?";
    Log.i("query", query);
    db.rawQuery(query, new String[] { String.valueOf(userID) });
}

通过这种方式，总未读消息将传递给表。

Android增量数据库值减一

2 个答案: