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DR,OP 表的时候，其他用户对此表的权限并没用被收回，这样导致重新创建同名的表时，以前其他用户对此表的权限会自动赋予，进而产生 权限外流。因此，在删除表时，要同时取消其他用户在此表上的相应权限。
下面的例子说明了不收回相关访问授权的隐患。
（1）用 root 创建用户 z1，授权对 test1 下所有表的 select 权限：
mysql> grant select on test1.* to z1@localhost;Query OK, 0 rows affected (0.00 sec) mysql> show grants for z1@localhost; +-----------------------------------------------+ | Grants for z1@localhost | +-----------------------------------------------+ | GRANT USAGE ON *.* TO 'z1'@'localhost' | | GRANT SELECT ON `test1`.* TO 'z1'@'localhost' | +-----------------------------------------------+ 2 rows in set (0.00 sec)
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（2）z1 登录，测试权限：
[root@localhost test1]# mysql -uz1 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 43 Server version: 5.0.41-community-log MySQL Community Edition (GPL) Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> use test1 Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed mysql> show tables; +-----------------+ | Tables_in_test1 | +-----------------+ | t1 | | t12 | | t2 | +-----------------+ 3 rows in set (0.00 sec)
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（3）root 登录，删除表 t1：
[root@localhost test1]# mysql -uroot ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO) [root@localhost test1]# mysql -uroot -p123 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 45 Server version: 5.0.41-community-log MySQL Community Edition (GPL) Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> use test1 Reading table information for completion of table and column namesYou can turn off this feature to get a quicker startup with -A Database changed mysql> drop table t1; Query OK, 0 rows affected (0.00 sec) mysql> exit Bye
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（4）z1 登录，再次测试权限:
[root@localhost test1]# mysql -uz1 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 46 Server version: 5.0.41-community-log MySQL Community Edition (GPL) Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> use test1 Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed mysql> show tables; +-----------------+ | Tables_in_test1 | +-----------------+ | t12 | | t2 | +-----------------+ 2 rows in set (0.00 sec)
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（5）此时 t1 表已经看不到了。
mysql> show grants for z1@localhost; +-----------------------------------------------+ | Grants for z1@localhost | +-----------------------------------------------+ | GRANT USAGE ON *.* TO 'z1'@'localhost' | | GRANT SELECT ON `test1`.* TO 'z1'@'localhost' | +-----------------------------------------------+ 2 rows in set (0.00 sec)
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权限仍然显示对 test1 下所有表的 SELECT（安全漏洞）。
（6）root 再次登录，创建 t1 条：
[root@localhost test1]# mysql -uroot -p123 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 48 Server version: 5.0.41-community-log MySQL Community Edition (GPL)Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> create table t1(id int); Query OK, 0 rows affected (0.03 sec) mysql> exit
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（7）z1 登录，对 t1 权限依旧存在：
[root@localhost test1]# mysql -uz1 test1 Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 49 Server version: 5.0.41-community-log MySQL Community Edition (GPL) Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show tables; +-----------------+ | Tables_in_test1 | +-----------------+ | t1 | | t12 | | t2 | +-----------------+ 3 rows in set (0.00 sec) mysql> select * from t1; Empty set (0.00 sec)
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注意：对表做删除后，其他用户对此表的权限不会自动收回，一定记住要手工收回。
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