突破MySQL视图限制：获取创建视图的SQL语句

创建视图的SQL包含了一个load_file()函数、为了使用该函数、必须满足下面所有条件：

视图本质上只是一条SQL语句而已、但令人蛋疼的是MySQL并没有把该SQL语句存储下来
而是像对待表一样、把视图的定义用文件的形式保存、以 .frm 存在
那么用show create view 显示的SQL将非常不友好

下面介绍一种方法来突破这种限制

创建视图：

mysql> create view v_t as select id from t where id=2;
Query OK, 0 rows affected (0.03 sec)

到相应目录查找视图定义文件：

[mysql@obe11g test]$ pwd
/home/mysql/mysql/data/test
[mysql@obe11g test]$ ls -alh
total 128K
drwxr-xr-x 2 mysql dba 4.0K Jul 27 19:45 .
drwxr-xr-x 5 mysql dba 4.0K Jul 27 19:13 ..
-rw-r--r-- 1 mysql dba 65 Jun 19 10:20 db.opt
-rw-rw---- 1 mysql dba 8.4K Jul 24 19:58 t.frm
-rw-rw---- 1 mysql dba 96K Jul 27 19:44 t.ibd
-rwxrwxrwx 1 mysql dba 451 Jul 27 19:45 v_t.frm

先用 show create view查询：

mysql> show create view v_t;
+------+----------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View | character_set_client | collation_connection |
+------+----------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| v_t | CREATE ALGORITHM=UNDEFINED DEFINER=`waterbin`@`localhost` SQL SECURITY DEFINER VIEW `v_t` AS select `t`.`id` AS `id` from `t` where (`t`.`id` = 2) | utf8 | utf8_general_ci |
+------+----------------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
1 row in set (0.00 sec)

会发现包含大量转义符、引号、没有代码格式化、没有注释、没有缩进等等、可读性很差、无法快速拷贝进行重建视图

查询创建视图的SQL语句：

SELECT
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
SUBSTRING_INDEX(LOAD_FILE('/home/mysql/mysql/data/test/v_t.frm'),
'\nsource=',-1),
'\\_','\_'), '\\%','\%'), '\\\\','\\'), '\\Z','\Z'), '\\t','\t'),
'\\r','\r'), '\\n','\n'), '\\b','\b'), '\\\"','\"'), '\\\'','\''),
'\\0','\0')
AS source;

输出结果、第一行便是该SQL：

+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| source |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| select id from t where id=2
client_cs_name=utf8
connection_cl_name=utf8_general_ci
view_body_utf8=select `test`.`t`.`id` AS `id` from `test`.`t` where (`test`.`t`.`id` = 2)
|
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

创建视图的SQL包含了一个load_file()函数、为了使用该函数、必须满足下面所有条件：

① the file must be located on the server host

② you must specify the full path name to the file

③ you must have the FILE privilege

验证：select user,file_priv from mysql.user;

④ The file must be readable by all

提醒：这里的all、不仅是OWNER、GROUP；还特指OTHERE！！

⑤ its size less than max_allowed_packet bytes

⑥ If the secure_file_priv system variable is set to a nonempty directory name

the file to be loaded must be located in that directory

相关阅读：

MySQL视图表创建与修改

MySQL视图(view)