Question

# 下面二条命令的结果显示是一样
mysql> show tables;
mysql> show tables from mysql;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| component                 |
| db                        |
| default_roles             |
| engine_cost               |
| func                      |
| general_log               |
| global_grants             |
| gtid_executed             |
| help_category             |
| help_keyword              |
| help_relation             |
| help_topic                |
| innodb_index_stats        |
| innodb_table_stats        |
| password_history          |
| plugin                    |
| procs_priv                |
| proxies_priv              |
| role_edges                |
| server_cost               |
| servers                   |
| slave_master_info         |
| slave_relay_log_info      |
| slave_worker_info         |
| slow_log                  |
| tables_priv               |
| time_zone                 |
| time_zone_leap_second     |
| time_zone_name            |
| time_zone_transition      |
| time_zone_transition_type |
| user                      |
+---------------------------+
33 rows in set (0.00 sec)

mysql> SELECT table_name, table_type, engine
       FROM information_schema.tables
       WHERE table_schema = 'mysql'
       ORDER BY table_name;
+---------------------------+------------+--------+
| TABLE_NAME                | TABLE_TYPE | ENGINE |
+---------------------------+------------+--------+
| columns_priv              | BASE TABLE | InnoDB |
| component                 | BASE TABLE | InnoDB |
| db                        | BASE TABLE | InnoDB |
| default_roles             | BASE TABLE | InnoDB |
| engine_cost               | BASE TABLE | InnoDB |
| func                      | BASE TABLE | InnoDB |
| general_log               | BASE TABLE | CSV    |
| global_grants             | BASE TABLE | InnoDB |
| gtid_executed             | BASE TABLE | InnoDB |
| help_category             | BASE TABLE | InnoDB |
| help_keyword              | BASE TABLE | InnoDB |
| help_relation             | BASE TABLE | InnoDB |
| help_topic                | BASE TABLE | InnoDB |
| innodb_index_stats        | BASE TABLE | InnoDB |
| innodb_table_stats        | BASE TABLE | InnoDB |
| password_history          | BASE TABLE | InnoDB |
| plugin                    | BASE TABLE | InnoDB |
| procs_priv                | BASE TABLE | InnoDB |
| proxies_priv              | BASE TABLE | InnoDB |
| role_edges                | BASE TABLE | InnoDB |
| server_cost               | BASE TABLE | InnoDB |
| servers                   | BASE TABLE | InnoDB |
| slave_master_info         | BASE TABLE | InnoDB |
| slave_relay_log_info      | BASE TABLE | InnoDB |
| slave_worker_info         | BASE TABLE | InnoDB |
| slow_log                  | BASE TABLE | CSV    |
| tables_priv               | BASE TABLE | InnoDB |
| time_zone                 | BASE TABLE | InnoDB |
| time_zone_leap_second     | BASE TABLE | InnoDB |
| time_zone_name            | BASE TABLE | InnoDB |
| time_zone_transition      | BASE TABLE | InnoDB |
| time_zone_transition_type | BASE TABLE | InnoDB |
| user                      | BASE TABLE | InnoDB |
+---------------------------+------------+--------+
33 rows in set (0.00 sec)

表格 1 mysql 库里的表详细说明

表名	表中文名	表简介
columns_priv	列权限
component	组件	5.7 新增
db	数据库
default_roles	缺省角色	5.7 新增
engine_cost	引擎开销
event	事件
func	函数
general_log	常规日志
global_grants	全局授权	5.7 新增
gtid_executed		5.7 新增
help_category	帮助分类
help_keyword	帮助关键词
help_relation	帮助关系
help_topic	帮助主题
innodb_index_stats	innodb 引擎索引统计
innodb_table_stats	innodb 表状态
ndb_binlog_index		5.7 删除
password_history	密码历史	5.7 新增
plugin	插件
proc	进程
procs_priv	进程权限
proxies_priv	代理权限
role_edges		5.7 新增
server_cost	服务器开销	5.7 新增
servers	服务器
slave_master_info	主从信息
slave_relay_log_info
slave_worker_info	从服务器 worker 信息
slow_log	慢 SQL 日志
tables_priv	表权限
time_zone	时区
time_zone_leap_second	时区闰秒
time_zone_name	时区名称
time_zone_transition	时区转换
time_zone_transition_type	时区转换类型
user	用户	存储用户名、密码、访问限制、增删改查等权限