确保子记录的序列号从1开始

Question

在SQL Server 2008 R2数据库上，这是一个很难的（我认为）。我有一个NotificationTemplate与零对多NotificationSmsTemplate子对象，因为我们的短信限制为160个字符的消息，我需要发送几个短信顺序传递整个短信通信。每NotificationTemplate，每个NotificationSmsTemplate具有SmsSequenceNumber属性。此号码可以是任何东西，只要它包含NotificationTemplate即可。

我如何能确保序列号开始11且连续来回NotificationSmsTemplate对象的集合含有NotificationTemplate。我只能想到使用内部序列号来允许用户在屏幕上订购模板，然后按顺序排序，在插入数据库时​​生成可见的序列号。

Answer 1

如果我正确理解您的要求，那么当AUTO_INCREMENT列是MyISAM表中多列索引的一部分时，您可以利用MySQL重用AUTO_INCREMENT值的方式。有关更多详细信息，请参见Using AUTO_INCREMENT。

下面是一个例子来说明我的意思：

创建一个表来保存您的通知模板：

CREATE TABLE IF NOT EXISTS `notification_template` (
    `id` INT NOT NULL AUTO_INCREMENT , 
    `notification` TEXT NOT NULL , 
    PRIMARY KEY (`id`)) 
ENGINE = MyISAM; 

创建一个表来保存的短信模板：

CREATE TABLE IF NOT EXISTS `notification_sms_template` (
    `notification_template_id` INT NOT NULL , 
    `sms_sequence_number` INT NOT NULL AUTO_INCREMENT , 
    `sms` VARCHAR(160) NOT NULL , 
    PRIMARY KEY (`notification_template_id`, `sms_sequence_number`)) 
ENGINE = MyISAM; 

插入notification_template表格中的几段长文本段落：

INSERT INTO `notification_template` (`id`, `notification`) VALUES 
(1, 'Tell me, O Muse, of that ingenious hero who travelled far and wide after he had sacked the famous town of Troy. Many cities did he visit, and many were the nations with whose manners and customs he was acquainted; moreover he suffered much by sea while trying to save his own life and bring his men safely home; but do what he might he could not save his men, for they perished through their own sheer folly in eating the cattle of the Sun-god Hyperion; so the god prevented them from ever reaching home. Tell me, too, about all these things, oh daughter of Jove, from whatsoever source you may know them.'), 
(2, 'There were once a man and a woman who had long in vain wished for a child. At length the woman hoped that God was about to grant her desire. These people had a little window at the back of their house from which a splendid garden could be seen, which was full of the most beautiful flowers and herbs. It was, however, surrounded by a high wall, and no one dared to go into it because it belonged to an enchantress, who had great power and was dreaded by all the world.'); 

插入160个字符的数据块到notification_sms_template表，指定notification_template的id其所涉及：

INSERT INTO `notification_sms_template` (`notification_template_id`, `sms`) VALUES 
(1, 'Tell me, O Muse, of that ingenious hero who travelled far and wide after he had sacked the famous town of Troy. Many cities did he visit, and many were the nat'), 
(1, 'ions with whose manners and customs he was acquainted; moreover he suffered much by sea while trying to save his own life and bring his men safely home; but do'), 
(1, ' what he might he could not save his men, for they perished through their own sheer folly in eating the cattle of the Sun-god Hyperion; so the god prevented th'), 
(1, 'em from ever reaching home. Tell me, too, about all these things, oh daughter of Jove, from whatsoever source you may know them.'), 
(2, 'There were once a man and a woman who had long in vain wished for a child. At length the woman hoped that God was about to grant her desire. These people had a'), 
(2, ' little window at the back of their house from which a splendid garden could be seen, which was full of the most beautiful flowers and herbs. It was, however, '), 
(2, 'surrounded by a high wall, and no one dared to go into it because it belonged to an enchantress, who had great power and was dreaded by all the world.'); 

如果现在选择从notification_sms_template的的ID，你会看到，sms_sequence_number从1开始对于每个notification_template：

SELECT `notification_template_id`, `sms_sequence_number` 
FROM `notification_sms_template`; 

+--------------------------+---------------------+ 
| notification_template_id | sms_sequence_number | 
+--------------------------+---------------------+ 
|      1 |     1 | 
|      1 |     2 | 
|      1 |     3 | 
|      1 |     4 | 
|      2 |     1 | 
|      2 |     2 | 
|      2 |     3 | 
+--------------------------+---------------------+