今儿有位同事提出，一套MySQL 5.6的环境，从数据库服务器本地登录，一切正常，可是若从远程服务器访问，就会报错，
ERROR 1045 (28000): Access denied for user 'bisal'@'x.x.x.x' (using password: YES)
我才开始接触MySQL，因此每一个错误场景，都是增长经验的机会，这种错误要么是密码错误，要么是未设置远程IP访问权限。
我们模拟下这个过程，首先，创建用户bisal，如果密码不加引号会报错，
mysql> create user bisal identified by bisal;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'bisal' at line 1
创建完成，可以看出，用户bisal的host是%，不是具体某个IP，
mysql> create user bisal identified by 'bisal';
Query OK, 0 rows affected (0.00 sec)
mysql> select user, password, host from user;
+-------+-------------------------------------------+-----------------+
| user | password | host |
+-------+-------------------------------------------+-----------------+
...
| bisal | *9AA096167EB7110830776F0438CEADA9A7987E31 | % |+-------+-------------------------------------------+-----------------+
实验一：让指定IP访问数据库
假设数据库服务器IP是x.x.x.1，授权让x.x.x.3用户可以访问，
mysql> grant all privileges on *.* to 'bisal'@'x.x.x.3';
Query OK, 0 rows affected (0.00 sec)
此时从x.x.x.2上访问数据库，就会提示错误，因为仅允许x.x.x.3服务器，可以访问数据库，
mysql -h x.x.x.1 -ubisal
ERROR 1045 (28000): Access denied for user 'bisal'@'app' (using password: YES)
授权让x.x.x.2用户可以访问，
mysql> grant all privileges on *.* to 'bisal'@'x.x.x.2' identified by 'bisal';
Query OK, 0 rows affected (0.00 sec)
此时从x.x.x.2上，就可以访问数据库了，
mysql -h x.x.x.1 -ubisal -pbisal
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 1008
Server version: 5.6.31-log MySQL Community Server (GPL)
Copyright (c) 2000, 2016, 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> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
实验二：让所有IP访问数据库
首先，收回刚才的授权，
mysql> revoke all privileges on *.* from bisal@'%';
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for bisal;
+--------------------------------------------------------------------------------------------+
| Grants for bisal@% |
+--------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'bisal'@'%' IDENTIFIED BY PASSWORD '*9AA096167EB7110830776F0438CEADA9A7987E31' |
+--------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
此时从x.x.x.2访问数据库，会提示错误，
mysql -h x.x.x.x -ubisal -pbisal
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 997
Server version: 5.6.31-log MySQL Community Server (GPL)
Copyright (c) 2000, 2016, 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> use mysql
ERROR 1044 (42000): Access denied for user 'bisal'@'%' to database 'mysql'
此时授予%所有机器访问权限，
mysql> grant all privileges on *.* to 'bisal'@'%' identified by 'bisal';
Query OK, 0 rows affected (0.00 sec)
从x.x.x.2访问数据库，此处的报错，是因为未输入密码，
mysql -ubisal
ERROR 1045 (28000): Access denied for user 'bisal'@'localhost' (using password: YES)
但如果之前设置的密码，和输入的密码不同，还是会提示错误，
mysql> grant all privileges on *.* to 'bisal'@'%' identified by '123';
Query OK, 0 rows affected (0.00 sec)
[root@vm-kvm11853-app ~]# mysql -h x.x.x.129 -ubisal -pbisal
Warning: Using a password on the command line interface can be insecure.
ERROR 1045 (28000): Access denied for user 'bisal'@'vm-kvm11853-app' (using password: YES)
使用正确的密码登录，一切正常了，
mysql -ubisal -p123
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 987
Server version: 5.6.31-log MySQL Community Server (GPL)
Copyright (c) 2000, 2016, 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> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
总结：
1. MySQL中可以设置某个IP访问权限，也可以设置%所有IP访问权限。、
2. grant all privileges ... identified by 'password'，此处的password可以不是这用户的密码，远程访问以这个密码为准。
3. create user设置密码，需要用引号括起来，否则会提示语法错误。
4. create user用户不加@信息，则默认创建的用户host是%。