从5.0到5.1，再到5.5，5.6，可以看到多了information_schema
完了是多了performance_schema ,里面内容不断增加，
这段时间学习oracle，还是世界上是最牛的数据库，发现里面的数据字典很牛，你想要的信息都能查到，很细，但是mysql就没有这么方便的途径了，比如说查进程，大家都知道show full processlist，但是5.0里面没有processlist这个表 ，你就没办法用sql 语句过滤进程，就比较头痛了。但是版本升级以后就不一样了。
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| KEY_COLUMN_USAGE |
| PROFILING |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| STATISTICS |
| TABLES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
+---------------------------------------+
5.1的 有28张表，多少11张
mysql> show tables;
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| ENGINES |
| EVENTS |
| FILES |
| GLOBAL_STATUS |
| GLOBAL_VARIABLES |
| KEY_COLUMN_USAGE |
| PARTITIONS |
| PLUGINS |
| PROCESSLIST |
| PROFILING |
| REFERENTIAL_CONSTRAINTS |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| SESSION_STATUS |
| SESSION_VARIABLES |
| STATISTICS |
| TABLES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
+---------------------------------------+
到了5.5， 猛增到40张了
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| ENGINES |
| EVENTS |
| FILES |
| GLOBAL_STATUS |
| GLOBAL_VARIABLES |
| KEY_COLUMN_USAGE |
| PARAMETERS |
| PARTITIONS |
| PLUGINS |
| PROCESSLIST |
| PROFILING |
| REFERENTIAL_CONSTRAINTS |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| SESSION_STATUS |
| SESSION_VARIABLES |
| STATISTICS |
| TABLES |
| TABLESPACES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
| INNODB_BUFFER_PAGE |
| INNODB_TRX |
| INNODB_BUFFER_POOL_STATS |
| INNODB_LOCK_WAITS |
| INNODB_CMPMEM |
| INNODB_CMP |
| INNODB_LOCKS |
| INNODB_CMPMEM_RESET |
| INNODB_CMP_RESET |
| INNODB_BUFFER_PAGE_LRU |
+---------------------------------------+
还多了个新的performance_schema
| cond_instances |
| events_waits_current |
| events_waits_history |
| events_waits_history_long |
| events_waits_summary_by_instance |
| events_waits_summary_by_thread_by_event_name |
| events_waits_summary_global_by_event_name |
| file_instances |
| file_summary_by_event_name |
| file_summary_by_instance |
| mutex_instances |
| performance_timers |
| rwlock_instances |
| setup_consumers |
| setup_instruments |
| setup_timers |
| threads
甲骨文似乎还抽出了MySQL的修订历史。修订历史将以前对无数行源代码进行的修改进行了分组，归纳到所谓的“变化集”中。一个变化集可以显示出某项具体功能发生的变化。它可以显示出修改者的身份、修改的时间和原因。
可以看到在oracle的管理下，mysql 一直在前行，有人说什么被收购以后越来越闭源了，但是对于普通公司，用户来说，影响还是比较小的，我相信并没有会用到test框架和自己看源码的各个修订历史。