這個問題是微信群中網友關于MySQL權限的討論，有這么一個業務需求（下面是他的原話）：
因為MySQL的很多功能都依賴主鍵，我想用zabbix用戶，來監控業務資料庫的所有表，是否都建立了主鍵，
監控的陳述句是：
SELECT COUNT(*)
FROM information_schema.tables t1 LEFT OUTER JOIN information_schema.table_constraints t2
ON t1.table_schema = t2.table_schema AND t1.table_name = t2.table_name AND t2.constraint_name IN ( 'PRIMARY' )
WHERE t2.table_name IS NULL
AND t1.table_schema NOT IN ( 'information_schema', 'myawr', 'mysql',
'performance_schema', 'slowlog', 'sys', 'test' )
AND t1.table_type = 'BASE TABLE'
但是我不希望zabbix用戶，能讀取業務庫的資料，一旦不給zabbix用戶讀取業務庫資料的權限，那么information_schema.TABLES 和 information_schema.TABLE_CONSTRAINTS 就不包含業務庫的表資訊了，也就統計不出來業務庫的表是否有建主鍵，有沒有什么辦法，即讓zabbix不能讀取業務庫資料，又能監控是否業務庫的表沒有建立主鍵？
首先，我們要知道一個事實：information_schema下的視圖沒法授權給某個用戶，如下所示
mysql> GRANT SELECT ON information_schema.TABLES TO test@'%';
ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema'
關于這個問題，可以參考mos上這篇文章：Why Setting Privileges on INFORMATION_SCHEMA does not Work (檔案 ID 1941558.1)
APPLIES TO:
MySQL Server - Version 5.6 and later
Information in this document applies to any platform.
GOAL
To determine how MySQL privileges work for INFORMATION_SCHEMA.
SOLUTION
A simple GRANT statement would be something like:
mysql> grant select,execute on information_schema.* to 'dbadm'@'localhost';
ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema'
The error indicates that the super user does not have the privileges to change the information_schema access privileges.
Which seems to go against what is normally the case for the root account which has SUPER privileges.
The reason for this error is that the information_schema database is actually a virtual database that is built when the service is started.
It is made up of tables and views designed to keep track of the server meta-data, that is, details of all the tables, procedures etc. in the database server.
So looking specifically at the above command, there is an attempt to add SELECT and EXECUTE privileges to this specialised database.
The SELECT option is not required however, because all users have the ability to read the tables in the information_schema database, so this is redundant.
The EXECUTE option does not make sense, because you are not allowed to create procedures in this special database.
There is also no capability to modify the tables in terms of INSERT, UPDATE, DELETE etc., so privileges are hard coded instead of managed per user.
那么怎么解決這個授權問題呢？ 直接授權不行，那么我們只能繞過這個問題，間接實作授權，思路如下：首先創建一個存盤程序（用戶資料庫），此存盤程序找出沒有主鍵的表的數量，然后將其授予test用戶，
DELIMITER //CREATE DEFINER=`root`@`localhost` PROCEDURE `moitor_without_primarykey`()
BEGINSELECT COUNT(*)
FROM information_schema.tables t1 LEFT OUTER JOIN information_schema.table_constraints t2
ON t1.table_schema = t2.table_schema AND t1.table_name = t2.table_name AND t2.constraint_name IN ( 'PRIMARY' )
WHERE t2.table_name IS NULL
AND t1.table_schema NOT IN ( 'information_schema', 'myawr', 'mysql',
'performance_schema', 'slowlog', 'sys', 'test' )
AND t1.table_type = 'BASE TABLE';
END //
DELIMITER ;
mysql> GRANT EXECUTE ON PROCEDURE moitor_without_primarykey TO 'test'@'%';
Query OK, 0 rows affected (0.02 sec)
此時test就能間接的去查詢information_schema下的物件了，
mysql> select current_user();
+----------------+
| current_user() |+----------------+
| test@% |
+----------------+
1 row in set (0.00 sec)
mysql> call moitor_without_primarykey;+----------+
| COUNT(*) |+----------+
| 6 |
+----------+
1 row in set (0.02 sec)
Query OK, 0 rows affected (0.02 sec)
查看test用戶的權限，
mysql> show grants for test@'%';
+-------------------------------------------------------------------------------+
| Grants for test@% |+-------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO `test`@`%` |
| GRANT EXECUTE ON PROCEDURE `zabbix`.`moitor_without_primarykey` TO `test`@`%` |
+-------------------------------------------------------------------------------+
2 rows in set (0.00 sec)
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標籤：MySQL
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