建立測試表
create table t1(id int);
create table t2(id int);
create table t3(id int);
create table t4(msg varchar(100));

如果授權的時候圖省事兒,使用萬用字元授權.
grant select,insert,update,delete on mvbox.* to 'xx'@'localhost' identified by 'xx';

如果以後需要回收某一張表許可權的時候,就會比較麻煩.
mysql> show grants for xx@'localhost';
+-----------------------------------------------------------------------------------------------------------+
| Grants for xx@localhost |
+-----------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'xx'@'localhost' IDENTIFIED BY PASSWORD '*B30134364A2D14319904C2C807363CF2C81ABD5B' |
| GRANT SELECT, INSERT, UPDATE, DELETE ON `mvbox`.* TO 'xx'@'localhost' |
+-----------------------------------------------------------------------------------------------------------+
2 rows in set (0.00 sec)

mysql> revoke insert on mvbox.t1 from xx@'localhost';
ERROR 1147 (42000): There is no such grant defined for user 'xx' on host 'localhost' on table 't1'
mysql>

因為授權是使用的萬用字元,回收也需要使用萬用字元.

如果需要回收t1表的insert許可權,可以使用如下的觸發器.

delimiter //
CREATE TRIGGER tri1 BEFORE INSERT ON t1 FOR EACH ROW
BEGIN
DECLARE msg varchar(100);
DECLARE cu varchar(40);
set cu=(select substring_index((select user()),'@',1)) ;
IF cu='xx' THEN
set msg = concat(cu,"You have no right to operate data!please connect DBAs");
SIGNAL SQLSTATE 'HY000' SET MESSAGE_TEXT = msg;
END IF;
END;
//
delimiter ;

這時,以xx登入,insert t1表則報錯如下
mysql> insert into t1 values(10);
ERROR 1644 (HY000): xx You have no right to operate data!please connect DBAs

這裡需要注意的是current_user,user函式,在觸發器呼叫的時候,返回的內容是不一樣的.
刪除原來的觸發器,新建一個觸發器測試

drop trigger tri1;
delimiter //
CREATE TRIGGER `tri2` BEFORE INSERT ON `t1` FOR EACH ROW
BEGIN
insert into t4 values(concat(current_user(),',',user(),',',session_user()));
END;
//
delimiter ;

使用xx使用者登入,執行如下命令
mysql> insert into t1 values(10);
Query OK, 1 row affected (0.00 sec)

mysql> select * from t4;
+------------------------------------------+
| msg |
+------------------------------------------+
| root@localhost,xx@localhost,xx@localhost |
+------------------------------------------+
1 row in set (0.00 sec)

可以發現在觸發器中,current_user()返回的是觸發器的定義者.
而user(),session_user()才是連線的使用者.

mysql>

MySQL回收某一授權

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