我只是不明白一件事。当我输入时：

SELECT table_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE';

我得到：

+----------------------------------------------+
| table_name                                   |
+----------------------------------------------+
| columns_priv                                 |
| db                                           |
| event                                        |
| func                                         |
| general_log                                  |
| help_category                                |
| help_keyword                                 |
| help_relation                                |
| help_topic                                   |
| host                                         |
| ndb_binlog_index                             |
| plugin                                       |
| proc                                         |
| procs_priv                                   |
| proxies_priv                                 |
| servers                                      |
| slow_log                                     |
| tables_priv                                  |
| time_zone                                    |
| time_zone_leap_second                        |
| time_zone_name                               |
| time_zone_transition                         |
| time_zone_transition_type                    |
| user                                         |
| 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                                      |
+----------------------------------------------+
41 rows in set (0.23 sec)

但是选择似乎根本不起作用：

mysql> select * from db;
ERROR 1109 (42S02): Unknown table 'db' in information_schema
mysql>

那怎么可能？我的意思是，SELECT table_name FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE';表明存在一个名为“ db”的表…

其次，当我键入：SELECT table_name FROM INFORMATION_SCHEMA.TABLES;它给我：

+----------------------------------------------+
| table_name                                   |
+----------------------------------------------+
| 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                       |
| columns_priv                                 |
| db                                           |
| event                                        |
| func                                         |
| general_log                                  |
| help_category                                |
| help_keyword                                 |
| help_relation                                |
| help_topic                                   |
| host                                         |
| ndb_binlog_index                             |
| plugin                                       |
| proc                                         |
| procs_priv                                   |
| proxies_priv                                 |
| servers                                      |
| slow_log                                     |
| tables_priv                                  |
| time_zone                                    |
| time_zone_leap_second                        |
| time_zone_name                               |
| time_zone_transition                         |
| time_zone_transition_type                    |
| user                                         |
| 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                                      |
+----------------------------------------------+
81 rows in set (0.00 sec)

我能够做到： mysql> select * from events;我得到了一些结果。这是为什么？为什么我只能选择大写字母呢？而且，如何从information_schema仅以大写形式给出的表中进行选择？干杯

如果很重要：我以root用户身份登录到我的数据库。