从192.168.111.99上连接远程数据的时候报错：
[mysql@LVS01 mysql_5621]$ mysql -uroot -p123 -h192.168.111.10 -P 5621
Warning: Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'root'@'192.168.111.99' (using password: YES
查看远程主机权限：
mysql> use mysql;
Database changed
mysql> select user,host,password from user;
+-------+----------------+-------------------------------------------+
| user | host | password |
+-------+----------------+-------------------------------------------+
| root | localhost | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | mysql-svr1 | |
| root | 127.0.0.1 | |
| root | ::1 | |
| repl | 192.168.110.20 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.20 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.30 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.10 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| user1 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.20 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.30 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.10 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| admin | 192.168.111.10 | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| root | 192.168.111.% | |
| root | 192.168.111.99 | |
| root | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
+-------+----------------+-------------------------------------------+
16 rows in set (0.00 sec)
发现已经给192.168.111.99授权了，可为什么还是连不上?
和192.168.111.99相关的权限是下面几行：
| root | 192.168.111.% | |
| root | 192.168.111.99 | |
| root | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
尝试使用空密码登陆成功：
[mysql@LVS01 mysql_5621]$ mysql -uroot -h192.168.111.10 -P 5621
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 20216
Server version: 5.6.21-log Source distribution
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
删除密码为空的用户：
mysql> drop user root@'192.168.111.%';
Query OK, 0 rows affected (0.31 sec)
mysql> drop user root@'192.168.111.99';
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host,password from user;
+-------+----------------+-------------------------------------------+
| user | host | password |
+-------+----------------+-------------------------------------------+
| root | localhost | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | mysql-svr1 | |
| root | 127.0.0.1 | |
| root | ::1 | |
| repl | 192.168.110.20 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.20 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.30 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| repl | 192.168.111.10 | *A424E797037BF97C19A2E88CF7891C5C2038C039 |
| user1 | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.20 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.30 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| root | 192.168.111.10 | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
| admin | 192.168.111.10 | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| root | % | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257 |
+-------+----------------+-------------------------------------------+
14 rows in set (0.00 sec)
mysql>
再次使用密码登陆成功：
[mysql@LVS01 mysql_5621]$ mysql -uroot -p123 -h192.168.111.10 -P 5621
Warning: Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 20312
Server version: 5.6.21-log Source distribution
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
总结：
出现这个错误的原因是同一个用户有不同主机范围的权限时，按最匹配的一个主机验证权限。
也就是说从192.168.111.99登陆服务器时，验证顺序为：
root@'192.168.111.99'
root@'192.168.111.%'
root@'%'
参考文档：
http://dev.mysql.com/doc/refman/5.7/en/connection-access.html
When multiple matches are possible, the server must determine which of them to use. It resolves this issue as follows:
Whenever the server reads the user table into memory, it sorts the rows.
When a client attempts to connect, the server looks through the rows in sorted order.
The server uses the first row that matches the client host name and user name.
The server uses sorting rules that order rows with the most-specific Host values first. Literal host names and IP addresses are the most specific. (The specificity of a literal IP address is not affected by whether it has a netmask, so 192.168.1.13 and 192.168.1.0/255.255.255.0 are considered equally specific.) The pattern '%' means “any host” and is least specific. The empty string '' also means “any host” but sorts after '%'. Rows with the same Host value are ordered with the most-specific User values first (a blank User value means “any user” and is least specific). For rows with equally-specific Host and User values, the order is indeterminate.
建议：
（1）用户授权时，按最小主机范围授权，并且赋予密码，只授权一次。
（2）如果将来主机范围变化，重新授权时可删除旧授权，否则可能因为两次授权密码不同导致类似问题。
