Mysql服务器如何得到最佳性能优化
My favorite question during Interview for people to work as MySQL DBAs or be involved with MySQL Performance in some way is to ask them what should be tuned in MySQL Server straight after installation, assuming it was installed with default settings.
在面试MySQL DBA或者那些打算做MySQL性能优化的人时，我最喜欢问题是：MySQL服务器按照默认设置安装完之后，应该做哪些方面的调节呢？
I’m surprised how many people fail to provide any reasonable answer to this question, and how many servers are where in wild which are running with default settings.
令我很惊讶的是，有多少人对这个问题无法给出合理的答案，又有多少服务器都运行在默认的设置下。
Even though you can tune quite a lot of variables in MySQL Servers only few of them are really important for most common workload. After you get these settings right other changes will most commonly offer only incremental performance improvements.
尽管你可以调节很多MySQL服务器上的变量，但是在大多数通常的工作负载下，只有少数几个才真正重要。如果你把这些变量设置正确了，那么修改其他变量最多只能对系统性能改善有一定提升。
key_buffer_size - Very important if you use MyISAM tables. Set up to 30-40% of available memory if you use MyISAM tables exclusively. Right size depends on amount of indexes, data size and workload - remember MyISAM uses OS cache to cache the data so you need to leave memory for it as well, and data can be much larger than indexes in many cases. Check however if all of key_buffer is used over time - it is not rare to see key_buffer being set to 4G while combined size of .MYI files is just 1GB. This would be just a waste. If you use few MyISAM tables you’ll want to keep it lower but still at least 16-32Mb so it is large enough to accommodate indexes for temporary tables which are created on disk.
key_buffer_size - 这对MyISAM表来说非常重要。如果只是使用MyISAM表，可以把它设置为可用内存的 30-40%。合理的值取决于索引大小、数据量以及负载 — 记住，MyISAM表会使用操作系统的缓存来缓存数据，因此需要留出部分内存给它们，很
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Class.forName("com.mySQL.jdbc.Driver");
String strUrl="jdbc:mysql://localhost:3306/stu?useUnicode=true&characterEncoding=GB2312";
String strUser="nuey";
String strPassword="password";
Connection conn=DriverManager.getCon ......
MySQL服务器包含一些其他SQL DBMS中不具备的扩展。注意，如果使用了它们，将无法把代码移植到其他SQL服务器。在某些情况下，你可以编写包含MySQL扩展的代码，但仍保持其可移植性，方法是用“/*... */”注释掉这些扩展。MySQL服务器能够解析并执行注释中的代码，就像对待其他MySQL语句一样，但其他SQL服务器将忽略 ......
数据库操作类：DBCommon.class.php
//---------------------------------------------------------------------
// MySQL Master/Slave数据库读写操作类
//
// 开发作者: heiyeluren
// 版本历史:
// 2006-09-20 基本单数据库操作功能, 25 个接口
// 2007-07-30 支持� ......
LAST_INSERT_ID
自动返回最后一个 INSERT 或 UPDATE 操作为 AUTO_INCREMENT 列设置的第一个发生的值. 参考这里
The ID that was generated is maintained in the server on a per-connection basis.
LAST_INSERT_ID是基于单个connection的, 不可能被其它的客户端连接改变。
可以用 SELECT LAST_INSERT_ID(); 查询LAST ......
