以下英文引自（cenalulu的技术博客）
The MySQL naming scheme uses release names that consist of three numbers and a suffix; for example, mysql-4.1.2-alpha. The numbers within the release name are interpreted like this:
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The first number (4) is the major version and also describes the file format. All Version 4 releases have the same file format.
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The second number (1) is the release level. Taken together, the major version and release level constitute the release series number.
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The third number (2) is the version number within the release series. This is incremented for each new release. Usually you want the latest version for the series you have chosen.
For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased.
Release names also include a suffix to indicate the stability level of the release. Releases within a series progress through a set of suffixes to indicate how the stability level improves. The possible suffixes are:
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alpha indicates that the release contains some large section of new code that hasn't been 100% tested. Known bugs (usually there are none) should be documented in the News section of the online manual at http://dev.mysql.com/doc/mysql/en/News.html. There are also new commands and extensions in most alpha releases. Active development that may involve major code changes can occur in an alpha release, but everything will be tested before issuing a release. For this reason, there should be no known bugs in any MySQL release.
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beta means that all new code has been tested. No major new features that could cause corruption in old code are added. There should be no known bugs. A version changes from alpha to beta when there haven't been any reported fatal bugs within an alpha version for at least a month and we have no plans to add any features that could make any old command unreliable.
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gamma is a beta that has been around a while and seems to work fine. Only minor fixes are added. This is what many other companies call a release.
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If there is no suffix, it means that the version has been run for a while at many different sites with no reports of bugs other than platform-specific bugs. Only critical bugfixes are applied to the release. This is what we call a production (stable) release.
以下为翻译，欢迎指正错误
MySQL 的命名是根据发行版本不同由三个数字和一个后缀组成，如：mysql-4.1.2-alpha。发行版名称中的数字使用如下规则解析：
- 第一个数字（4）表示主版本（major version），它同时也定义了文件格式（file format）。所有主版本为4的版本有着同样的文件格式；
- 第二个数字（1）表示发行版本（release level），主版本和发行版本一同构成该发行版序列号（series number）；
- 第三个数字（2）表示该发行版系列的次版本（version），该数字随着发行版本的每次新释放递增，通常我们应该选择最新的次版本。
每次软件有较小的改动时，最后一个数字都会递增。当软件新增功能或相较之前发行的版本有任何不兼容时，第二个数字就会递增。当文件格式发生变化时，第一个数字增加。
发行版名称中包含一个后缀用以标示该发行版的稳定性，每一发行版都会包含一个特定标示，标示此次发行版相对之前发行版的稳定程度，这些后缀包括：
- alpha 表示相对于之前的发行版本，该发行版有较多代码改动，且未经 100% 测试。所有已知的漏洞（通常不会有）都会在在线手册http://dev.mysql.com/doc/mysql/en/News.html上以单独的版块列出。通常在alpha版本中也会加入一些新的命令和扩展，当前正在进行的开发也可能会对alpha版本的主要代码进行修改，但所有的更改都会经过测试，基于这种形式，一般在新发行的版本中不会引入新的漏洞；
- beta 表示所有新代码都已经过测试，新增代码和功能不会引起系统崩溃，系统中没有已知的漏洞。一般alpha版本在发行后一个月内没有接收到致命错误报告才会升级为beta版本，同时也不会再增加任何可能给系统带来新的不稳定因素的功能；
- gamma 版是当beta版经过短期时间运行后并没有发现任何问题时释出的版本，通常只会做一些很小的修正。这在很多公司往往正式作为发行版了；
- 如果没有后缀，则表示该版本已经在众多站点稳定运行一段时间并且么有任何漏洞报告（除了在特定系统平台上才会出现的漏洞），一般只会对该版本做致命性错误的修改。这就是通常所说的稳定版（stable）。
