mariadb 状态明智 where case 子句在视图中

问题描述

我在协作表中创建了以下视图

CREATE VIEW contents(
  id,title
)
AS
select 
   mytable.id as id,mytable.title as title
from mytable 
where mytable.owner = substring_index(user(),'@',1);

有什么方法可以检测视图内部的当前状态，例如 where 子句中的 select,insert,update,delete 吗？

我希望像下面这样，不知道如何在 MysqL/mariadb 中生成等价物

/* during select statement user can see all available data*/
if state == 'select' then
    where 1 = 1 /* can see all data */
else
/* if state is update or delete user is allowed to modify or delete data which for which he/she is owner*/
    where mytable.owner = substring_index(user(),1);
endif

Here is my sample data

MariaDB [test]> select * from mytable;
+----+-------------------+-------+
| id | title             | owner |
+----+-------------------+-------+
|  1 | created by root   | root  |
|  4 | created by helen  | helen |
|  6 | created by helen1 | helen |
|  7 | 123               | lina |
+----+-------------------+-------+

用户 helen 和 lina 拥有 SELECT,INSERT,UPDATE,DELETE 的内容视图授权

• 用户helen也是普通用户如何授予创建new_database的权限，并继承new_database中helen创建的任何新表的权限？我不想以管理员身份创建海伦。用户 helen 应该能够在她创建的数据库中创建任意数量的数据库和表。这是否可能？

   new_database
         table1
         table2
         .....
         .....
         tableN

解决方法

因为 check constrants 不能使用 user。您可以使用 TRIGGERS 来强制执行 fiddle 之类的约束：

插入：

CREATE TRIGGER enforce_insert
BEFORE
INSERT ON mytable
FOR EACH ROW
  IF NEW.owner != substring_index(user(),'@',1) THEN
    SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'conflict of owner on insert';
  END IF

更新：

CREATE TRIGGER enforce_update
BEFORE
UPDATE ON mytable
FOR EACH ROW
  IF OLD.owner != substring_index(user(),1)
     OR NEW.owner != substring_index(user(),1) THEN
    SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'conflict of owner on update';
  END IF

删除：

CREATE TRIGGER enforce_delete
BEFORE
DELETE ON mytable
FOR EACH ROW
  IF OLD.owner != substring_index(user(),1) THEN
    SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = 'conflict of owner on delete';
  END IF

但通常建议应用程序强制执行数据结构的示意图。

参考：trigger manual