创建测试表
create table t1(id int);
create table t2(id int);
create table t3(id int);
create table t4(msg varchar(100));

如果授权的时候图省事儿,使用通配符授权.
grant select,insert,update,delete on mvbox.* to 'xx'@'localhost' identified by 'xx';

如果以后需要回收某一张表权限的时候,就会比较麻烦.
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>

因为授权是使用的通配符,回收也需要使用通配符.

如果需要回收t1表的insert权限,可以使用如下的触发器.

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 ;

这时,以xx登录,insert t1表则报错如下
mysql> insert into t1 values(10);
ERROR 1644 (HY000): xx You have no right to operate data!please connect DBAs

这里需要注意的是current_user,user函数,在触发器调用的时候,返回的内容是不一样的.
删除原来的触发器,新建一个触发器测试

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用户登录,执行如下命令
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)

可以发现在触发器中,current_user()返回的是触发器的定义者.
而user(),session_user()才是连接的用户.

mysql>

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MySQL回收某一授权

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