如何在MySQL中生成动态序列表? [英] How to generate a dynamic sequence table in MySQL?

问题描述

我正在尝试在MySQL中生成序列表，以便可以从last_insert_id获取唯一ID.

I'm trying to generate a sequence table in MySQL, so that I can get unique ids from last_insert_id.

问题是我需要动态地处理多个序列.

The problem is that I need multiple sequences dynamically.

首先，我创建了一个表:

At the first, I created a table:

CREATE TABLE `sequence` (
  `label` char(30) CHARACTER SET latin1 NOT NULL,
  `id` mediumint(9) NOT NULL DEFAULT '0',
  PRIMARY KEY (`label`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8

然后尝试使用 http://dev.mysql.com/doc/refman/5.0/en/information-functions.html#function_last-insert-id

UPDATE sequence SET id = LAST_INSERT_ID(id + 1) WHERE label = 'test';
SELECT LAST_INSERT_ID();

一段时间后，我意识到我还需要安全地为新标签生成行. 因此，我将该模式更改为:

After a while I realized that I also need to generate rows for new labels safely. So I changed this schema into:

CREATE TABLE `sequence` (
  `label` char(30) CHARACTER SET latin1 NOT NULL,
  `id` mediumint(9) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`label`,`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8

我只是放弃了使用WHERE子句来更新其ID.

And I simply gave up using WHERE clause to update its id.

INSERT INTO sequence (label) values ( ? )
SELECT LAST_INSERT_ID()

这是正确的方法吗?我想知道是否有更好的解决方案.

Is this a proper way? I want to know if there is a better solution.

推荐答案

MyISAM引擎将为您完成-

The MyISAM engine will do it for you -

表定义:

CREATE TABLE `sequence` (
  `label` char(30) CHARACTER SET latin1 NOT NULL,
  `id` mediumint(9) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`label`,`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

填充表:

INSERT INTO sequence VALUES ('a', NULL); -- add some 'a' labels
INSERT INTO sequence VALUES ('a', NULL);
INSERT INTO sequence VALUES ('a', NULL);

INSERT INTO sequence VALUES ('b', NULL); -- add another labels 'b'
INSERT INTO sequence VALUES ('b', NULL);

INSERT INTO sequence VALUES ('a', NULL); -- add some 'a' labels
INSERT INTO sequence VALUES ('a', NULL);

显示结果:

SELECT * FROM sequence;
+-------+----+
| label | id |
+-------+----+
| a     |  1 |
| a     |  2 |
| a     |  3 |
| a     |  4 |
| a     |  5 |
| a     |  6 |
| b     |  1 |
| b     |  2 |
+-------+----+

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