mysql--user表

mysql数据库 用例：mysql 

mysql> show tables;
+---------------------------+
| Tables_in_mysql           |
+---------------------------+
| columns_priv              |
| db                        |
| event                     |
| func                      |
| general_log               |
| help_category             |
| help_keyword              |
| help_relation             |
| help_topic                |
| innodb_index_stats        |
| innodb_table_stats        |
| ndb_binlog_index          |
| plugin                    |
| proc                      |
| procs_priv                |
| proxies_priv              |
| 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                      |
+---------------------------+
28 rows in set (0.01 sec)

 mysql27张表中 user表保存登录mysql的用户信息

查看主键信息

SELECT
  t.TABLE_NAME,
  t.CONSTRAINT_TYPE,
  c.COLUMN_NAME,
  c.ORDINAL_POSITION
FROM
  INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS t,
  INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS c
WHERE
  t.TABLE_NAME = c.TABLE_NAME
  -- AND t.TABLE_SCHEMA = 数据库名称
  AND t.CONSTRAINT_TYPE = 'PRIMARY KEY' and c.TABLE_NAME='user';

　　

可是看到主键是user和host

查看数据

建host设为%可使任意客户端进行连接

客户端远程连接不到数据库

可能原因：

1、服务器防护墙开着 
2、user表问题 将user='' host=''

解决办法：
1、关闭防护墙
2、删除user='' and host=''记录