mysql当前用户user()与current |
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mysql当前用户user()与current
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Mysql在进行登陆时，会去匹配mysql库中的user表，并赋予相应的权限，但是怎么知道我们当时的登陆的用户名及相应的权限呢？ 在Mysql中，有两个函数，一个是user(),一个是current_user();
我们来运行一下看一下他们有什么区别： 
mysql> select user();
+----------------------+
| user() |
+----------------------+
| [email protected] |
+----------------------+
1 row in set (0.00 sec)
mysql> select current_user();
+------------------+
| current_user() |
+------------------+
| [email protected].%.% |
+------------------+
1 row in set (0.00 sec)
user()是用来显示当前登陆的用户名与它对应的host，帮助文档是这样描述的： Returns the current MySQL user name and host name as a string in theutf8 character set. currrent_user()是用来显示当前登陆用户对应在user表中的哪一个，帮助文档是这样描述的： Returns the user name and host name combination for the MySQL accountthat the server used to authenticate the current client. This accountdetermines your access privileges. The return value is a string in theutf8 character set.
所以假如我们想知道当前登陆的用户具有什么权限的话， 第一步是找出当前登陆用户是用user表中的哪一个，用current_user()
mysql> select current_user();
+------------------+
| current_user() |
+------------------+
| [email protected].%.% |
+------------------+
1 row in set (0.00 sec)
第二步用show grants命令，如下：
mysql> show grants for 'test'@'192.168.%.%';
+--------------------------------------------------------------------------------------------------------------------------------+
| Grants for [email protected].%.% |
+--------------------------------------------------------------------------------------------------------------------------------+
| GRANT SELECT, INSERT, UPDATE ON *.* TO 'test'@'192.168.%.%' IDENTIFIED BY PASSWORD '*032197AE5731D4664921A6CCAC7CFCE6A0698693' |
+--------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
好了，那另一个问题是，如果有如下的用户名，host及权限，我在登陆时到底会是匹配到哪一个呢？
mysql> grant select on *.* to [email protected] identified by '000000';
Query OK, 0 rows affected (0.00 sec)
mysql> grant select,update on *.* to 'test'@'192.168.203.%' identified by '000000';
Query OK, 0 rows affected (0.01 sec)
mysql> grant select,update,insert on *.* to 'test'@'192.168.%.%' identified by '000000';
Query OK, 0 rows affected (0.01 sec)
mysql> grant select,update,insert,delete on *.* to 'test'@'192.%.%.%' identified by '000000';
Query OK, 0 rows affected (0.00 sec)
mysql> grant update,insert,delete on *.* to 'test'@'%' identified by '000000';
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host from user order by user,host;
+-------------+-----------------+
| user | host |
+-------------+-----------------+
| root | localhost |
| test | % |
| test | 192.%.%.% |
| test | 192.168.%.% |
| test | 192.168.203.% |
| test | 192.168.203.132 |
+-------------+-----------------+
如果我用如下命令进行登陆，会匹配到user表中的哪一个？ 1 [root@host2 ~]# mysql -h192.168.203.132 -utest -p
我们可以用上面提到的select current_user()可以清楚地查找出来
mysql> select current_user();
+----------------------+
| user() |
+----------------------+
| [email protected] |
+----------------------+
1 row in set (0.00 sec)
我们删除对应的帐户： delete from user where user='test' and host='192.168.203.132'; 再次登陆： [root@host2 ~]# mysql -h192.168.203.132 -utest -p 此时：
mysql> select current_user();
+------------------+
| current_user() |
+------------------+
| [email protected].% |
+------------------+
1 row in set (0.00 sec)
继续删除 mysql> delete from user where user='test' and host='192.168.203.%'; 再登陆：
mysql> select current_user();
+------------------+
| current_user() |
+------------------+
| [email protected].%.% |
+------------------+
1 row in set (0.00 sec)
以上每一次执行后用user()都可以得到相同的结果：
mysql> select user();
+----------------------+
| user() |
+----------------------+
| [email protected] |
+----------------------+
1 row in set (0.00 sec)
所以结论是：mysql在登陆时会用最精确匹配user表中的帐户，host来作为当前的用户。 |
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