Question

出于某种原因，当我对MySQL中的特定表进行更新时，响应是：

＆＃34;匹配的行数：1已更改：0警告：0＆＃34;

我不能为我的生活找出原因。我可以从数据库中进行选择:(我有X＆＃39;输出敏感数据 - 它只是文本）

mysql> SELECT * FROM outgoings WHERE id=198;
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
| id  | user_id | outgoing_date | form | bsb | account_number | transfer_number | amount    | recipient                          | client_id | project_id | purpose          | created_at          | updated_at          | received_from | cheque_number | cheque_to | project_id_from | cheque_drawer                   | recipient_purpose | transferrer_purpose | client_id_from |
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
| 198 |       2 | 2015-03-11    |    3 |     |                |                 | 407481.25 | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |       162 |        503 | XXXXXXXXXXXXXXXX | 2015-03-13 17:51:36 | 2015-03-13 17:51:36 |               | 161           |           |            NULL | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |                   |                     |           NULL |
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
1 row in set (0.00 sec)

如您所见，金额列为407481.25。然后我运行一个简单的更新查询：

mysql> UPDATE cl_time.outgoings SET amount=407481.24 WHERE outgoings.id=198;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

结果显示没有更新，尽管事实上我实际上是想改变一些东西。如果我再次运行select查询，我会看到相同的结果：

mysql> SELECT * FROM outgoings WHERE id=198;
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
| id  | user_id | outgoing_date | form | bsb | account_number | transfer_number | amount    | recipient                          | client_id | project_id | purpose          | created_at          | updated_at          | received_from | cheque_number | cheque_to | project_id_from | cheque_drawer                   | recipient_purpose | transferrer_purpose | client_id_from |
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
| 198 |       2 | 2015-03-11    |    3 |     |                |                 | 407481.25 | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |       162 |        503 | XXXXXXXXXXXXXXXX | 2015-03-13 17:51:36 | 2015-03-13 17:51:36 |               | 161           |           |            NULL | XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |                   |                     |           NULL |
+-----+---------+---------------+------+-----+----------------+-----------------+-----------+------------------------------------+-----------+------------+------------------+---------------------+---------------------+---------------+---------------+-----------+-----------------+---------------------------------+-------------------+---------------------+----------------+
1 row in set (0.00 sec)

对于更多上下文，这是表结构：

CREATE TABLE `outgoings` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `outgoing_date` date NOT NULL,
  `form` int(11) NOT NULL,
  `bsb` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `account_number` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `transfer_number` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `amount` float(8,2) NOT NULL,
  `recipient` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `client_id` int(11) NOT NULL,
  `project_id` int(11) NOT NULL,
  `purpose` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `received_from` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `cheque_number` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `cheque_to` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `project_id_from` int(11) DEFAULT NULL,
  `cheque_drawer` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `recipient_purpose` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `transferrer_purpose` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `client_id_from` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `outgoings_user_id_index` (`user_id`),
  KEY `outgoings_client_id_index` (`client_id`),
  KEY `outgoings_project_id_index` (`project_id`),
  KEY `outgoings_project_id_from_index` (`project_id_from`),
  KEY `outgoings_client_id_from_index` (`client_id_from`)
) ENGINE=MyISAM AUTO_INCREMENT=228 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

最后，这个表的数据是由我在Laravel中编写的PHP应用程序插入并写入的。但是，应用程序永远不会在此表上运行更新查询。所有这一切都工作正常，直到我将应用程序迁移到新服务器，我现在无法运行我的更新。

哦，我的mysql版本是：5.5.41，在Ubuntu上运行。

（这些问题似乎要求大致相同，但是没有一个答案对我有用，所以我在这里询问我的所有数据：Why would rows match but not be changed with a mysql update statement?和Update statement in mysql not working, while it has to work）

Answer 1

更新不会更改行的值的原因是舍入问题。您已将amount定义为float(8,2)。然后，您将值从407481.25更改为407481.24 - 它们之间的差异仅为0.01，但我们知道计算机存在舍入问题。

由于更新没有写入新值，因此可以100％安全地得出结论，由于舍入问题，MySQL将这两个数字视为相同。如果记录没有真正改变，MySQL就不会把它写下来 - 这是一个优化步骤，如果没有必要，MySQL将不会让硬盘进入工作。

现在，这意味着您需要调整amount列类型并将其更改为整数，然后在内部将小数点向左移动两个位置或使用数据类型，例如{{1}具有较大的十进制数字最大数字（例如：decimal）。

Answer 2

在mysql更新中，当行中的值实际上没有改变时，它不会计入更改的行数（显然）。

＆＃34;变更＆＃34;意味着＆＃34;新值与旧值不同＆＃34;。

Answer 3

您可以将数据类型更改为DOUBLE：

alter table outgoings modify amount DOUBLE;

MySQL中的更新返回＆＃34;匹配的行数：1已更改：0警告：0＆＃34;

3 个答案: