今天在一个修改过权限的MySQL数据库遇到了“ERROR 1045 (28000): Access denied for user 'xxx'@'xxx.xxx.xxx.xxx' (using password: YES)”和“ERROR 1449 (HY000): The user specified as a definer ('xxx'@'xx') does not exist” 错误，花了点时间研究并重现该错误，并将其整理在此篇文章。
在测试数据库MyDB，我们创建了一个mydbadmin的账号，任意IP地址都可以访问该数据库，如下所示：
mysql> GRANT ALL PRIVILEGES ON `MyDB`.* TO 'mydbadmin'@'%' IDENTIFIED BY 'mydbadmin13s5';
Query OK, 0 rows affected (0.03 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
然后以这个mydbadmin登录数据库，创建一个视图v_student. 当然，你也可以创建存储过程或是函数等其他对象，它们也都会遇到这个错误。
mysql> desc student;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| stu_id | int(11) | YES | | NULL | |
| stu_name | varchar(12) | YES | | NULL | |
| sex | int(11) | YES | | NULL | |
| grade | int(11) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
5 rows in set (0.00 sec)
mysql> create or replace view v_student
-> as
-> select stu_name, sex, age
-> from student
-> where grade >=3;
Query OK, 0 rows affected (0.02 sec)
假如现在检查时发现任意IP都可以访问这个账号是不符合安全规范的，然后删除了这个账号（如果你用rename user 也会遇到这个问题），重建了该账号。此时你在较大权限的用户下就会遇到“ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist”错误。如下所示：
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> select user,host from mysql.user where user='mydbadmin';
+-----------+------+
| user | host |
+-----------+------+
| mydbadmin | % |
+-----------+------+
1 row in set (0.00 sec)
mysql>
mysql> drop user mydbadmin@'%';
Query OK, 0 rows affected (0.02 sec)
mysql> select count(*) from v_student;
ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist
mysql>
mysql> select user,host from mysql.user where user='mydbadmin';
Empty set (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> GRANT ALL PRIVILEGES ON `MyDB`.* TO 'mydbadmin'@'192.168.%' IDENTIFIED BY 'mydbadmin135';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql>
然后你以在客户端使用mydbadmin登录后，查询视图就会报“ERROR 1045 (28000): Access denied for user 'mydbadmin'@'192.168.%' (using password: YES)”
mysql> select user();
+-------------------------+
| user() |
+-------------------------+
| mydbadmin@192.168.7.43 |
+-------------------------+
1 row in set (0.01 sec)
mysql> select * from v_student;
ERROR 1045 (28000): Access denied for user 'mydbadmin'@'192.168.%' (using password: YES)
原因分析
出现这个问题，是因为账号mydbadmin@`%`已经不存在了。而视图指定DEFINER为mydbadmin@`%`，此时创建者不存在了。而SQL SECURITY也是DEFINER，所以MySQL认为现在的用户无权限访问该视图。所以有下面一些方法来解决这个错误。
解决方案
1：重建视图（存储过程或函数）即可解决问题。不过对于数据库视图很多的情况，这个方法略显笨拙和繁琐。
mysql> show create view v_student;
mysql> create or replace view v_student
-> as
-> select stu_name, sex, age
-> from student
-> where grade >=3;
Query OK, 0 rows affected (0.00 sec）
当然可以批量生成相关SQL，类似于下面SQL
SELECT CONCAT("alter DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW ",TABLE_SCHEMA,".",TABLE_NAME," as ",VIEW_DEFINITION,";")
FROM information_schema.VIEWS
WHERE DEFINER=''mydbadmin@%';
2：如果创建视图（存储过程或函数）时，使用SQL SECURITY INVOKER，就可以避免出现这种情况。
如下所示，创建视图时指定SQL SECURITY INVOKER.
SQL SECURITY { DEFINER | INVOKER } ：指明谁有权限来执行。默认情况下，系统指定为DEFINE.
DEFINER 表示按定义者拥有的权限来执行
INVOKER 表示用调用者的权限来执行。
mysql> use MyDB;
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
mysql> select user();
+-------------------------+
| user() |
+-------------------------+
| mydbadmin@192.168.7.218 |
+-------------------------+
1 row in set (0.00 sec)
mysql> create or replace definer='mydbadmin'@'%'
-> sql security invoker
-> view v_student
-> as
-> select stu_name, sex, age
-> from student
-> where grade >=3;
Query OK, 0 rows affected (0.00 sec)
删除用户mydbadmin@'%'，此时你会发现还能执行。
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> drop user mydbadmin@'%';
Query OK, 0 rows affected (0.00 sec)
mysql> select count(*) from v_student;
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.00 sec)
mysql>
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> GRANT ALL PRIVILEGES ON `MyDB`.* TO 'mydbadmin'@'192.168.%' IDENTIFIED BY 'mydbadmin135';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> select user();
+-------------------------+
| user() |
+-------------------------+
| mydbadmin@192.168.7.218 |
+-------------------------+
1 row in set (0.00 sec)
mysql> select count(*) from v_student;
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.00 sec)
mysql>
3：这种方法只针对于存储过程或函数 ，对于视图而言，由于information_schema.VIEWS是无法修改的。所以无法使用此方法。如下测试所示：
mysql> UPDATE information_schema.VIEWS
-> SET DEFINER='root@localhost'
-> WHERE TABLE_NAME='v_student';
ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema'
mysql> select user();
+-------------------------+
| user() |
+-------------------------+
| mydbadmin@192.168.7.34 |
+-------------------------+
1 row in set (0.00 sec)
mysql> use MyDB;
Database changed
mysql> DELIMITER &&
mysql> CREATE DEFINER='mydbadmin'@'%' PROCEDURE prc_my_test()
-> BEGIN
-> SELECT COUNT(*) FROM student;
-> END &&
Query OK, 0 rows affected (0.03 sec)
mysql> DELIMITER ;
mysql>
mysql> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> select db, name, type ,security_type, definer
-> from mysql.proc
-> where name='prc_my_test';
+------+-------------+-----------+---------------+-------------+
| db | name | type | security_type | definer |
+------+-------------+-----------+---------------+-------------+
| MyDB | prc_my_test | PROCEDURE | DEFINER | mydbadmin@% |
+------+-------------+-----------+---------------+-------------+
1 row in set (0.00 sec)
mysql> call prc_my_test();
+----------+
| COUNT(*) |
+----------+
| 0 |
+----------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> drop user mydbadmin@'%';
Query OK, 0 rows affected (0.01 sec)
mysql> call prc_my_test();
ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist
mysql> update mysql.proc set definer='root@localhost' where name='prc_my_test';
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select db, name, type ,security_type, definer
-> from mysql.proc
-> where name='prc_my_test';
+------+-------------+-----------+---------------+----------------+
| db | name | type | security_type | definer |
+------+-------------+-----------+---------------+----------------+
| MyDB | prc_my_test | PROCEDURE | DEFINER | root@localhost |
+------+-------------+-----------+---------------+----------------+
1 row in set (0.00 sec)
mysql> call prc_my_test();
ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> call prc_my_test();
ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist
mysql> exit
Bye
如上所示，必须退出重新登录，才能生效，如果更新完mysql.proc后，不退出当前会话，依然会报“ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist”错误。
root@DB-Server ~]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 43
Server version: 5.6.20-enterprise-commercial-advanced-log MySQL Enterprise Server - Advanced Edition (Commercial)
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> use MyDB;
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
mysql> call prc_my_test();
+----------+
| COUNT(*) |
+----------+
| 0 |
+----------+
1 row in set (0.01 sec)
Query OK, 0 rows affected (0.01 sec)
这种方法，对于存储过程或函数，意义在于可以批量修改，非常快捷方便。唯一比较遗憾的是对于VIEW，无法使用。
4： 重新创建账号'mydbadmin'@'%' ，不过像这个案例，本身是处于安全考虑，限制能够访问数据库的IP，那么此时这种方案就不太可行，如果只是误删用户，那么这种方案就比较有效。
mysql> drop user 'mydbadmin'@'%';
Query OK, 0 rows affected (0.00 sec)
mysql> select count(*) from v_student;
ERROR 1449 (HY000): The user specified as a definer ('mydbadmin'@'%') does not exist
mysql> GRANT ALL PRIVILEGES ON `MyDB`.* TO 'mydbadmin'@'%' IDENTIFIED BY 'mydbadmin13s5';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> select count(*) from v_student;
+----------+
| count(*) |
+----------+
| 0 |
+----------+
1 row in set (0.00 sec)
mysql>
另外，对于存储过程、函数、定时事件、视图，都可以参考上面方法进行，其中定时事件主要修改mysql.event下的表。
update mysql.event set definer='root@localhost';
参考资料：
http://kedar.nitty-witty.com/blog/solutions-mysql-error-1449-the-user-specified-as-a-definer-does-not-exist