正常解釋

%代表任何客戶機都可以連接
localhost代表只可以本機連接

一般情況能訪問本地數據庫的都是加了權限了，一般都是禁止別的機器訪問本地的mysql端口的，如果允許也是要加上指定ip才可以訪問，這樣才能保證數據庫不會被遠程訪問。

1 前言

操作MySQL的時候發現，有時只建了%的賬號，可以通過localhost連接，有時候卻不可以，網上搜索也找不到滿意的答案，干脆手動測試一波

2 兩種連接方法

這里說的兩種連接方法指是執行mysql命令時，-h參數填的是localhost還是IP, 兩種連接方式的區別如下

-h 參數為 localhost
當-h參數為localhost的時候，實際上是使用socket連接的（默認連接方式）, 實例如下

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -hlocalhost
Enter password:
========= 省略 ===========

mysql> status
/usr/local/mysql57/bin/mysql Ver 14.14 Distrib 5.7.21, for linux-glibc2.12 (x86_64) using EditLine wrapper

Connection id: 9
Current database:
Current user: test_user@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.21-log MySQL Community Server (GPL)
Protocol version: 10
Connection: Localhost via UNIX socket

從Current user可以看到用戶是xx@localhost, 連接方式為Localhost via UNIX socket

-h 參數為 IP

當-h參數為IP的時候，實際上是使用TCP連接的, 實例如下

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -h127.0.0.1
Enter password:
========= 省略 ===========

mysql> status
--------------
/usr/local/mysql57/bin/mysql Ver 14.14 Distrib 5.7.21, for linux-glibc2.12 (x86_64) using EditLine wrapper

Connection id: 11
Current database:
Current user: test_user@127.0.0.1
SSL: Cipher in use is DHE-RSA-AES256-SHA
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.21-log MySQL Community Server (GPL)
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP
Server characterset: utf8

從Current user可以看到用戶是xx@127.0.0.1, 連接方式為TCP/IP

3 不同版本的差別

測試方法就是看能不能連接，如果不想看測試過程可以拉到最后看結論

3.1 MySQL 8.0

創建用戶

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.11 |
+-----------+
1 row in set (0.00 sec)

mysql> create user test_user@'%' identified by 'test_user';
Query OK, 0 rows affected (0.07 sec)
使用 localhost 登錄
[root@mysql-test-72 ~]# /usr/local/mysql80/bin/mysql -utest_user -p -hlocalhost
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.11 MySQL Community Server - GPL
========= 省略 ===========

mysql> status
--------------
/usr/local/mysql80/bin/mysql Ver 8.0.11 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)

Connection id: 9
Current database:
Current user: test_user@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 8.0.11 MySQL Community Server - GPL
Protocol version: 10
Connection: Localhost via UNIX socket
...

使用 IP 登錄

[root@mysql-test-72 ~]# /usr/local/mysql80/bin/mysql -utest_user -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.11 MySQL Community Server - GPL
========= 省略 ===========

mysql> status
--------------
/usr/local/mysql80/bin/mysql Ver 8.0.11 for linux-glibc2.12 on x86_64 (MySQL Community Server - GPL)

Connection id: 8
Current database:
Current user: test_user@127.0.0.1
SSL: Cipher in use is DHE-RSA-AES128-GCM-SHA256
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 8.0.11 MySQL Community Server - GPL
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP

結果顯示8.0版本的MySQL, % 包括localhost

3.2 MySQL 5.7

創建 % 用戶

db83-3306>>create user test_user@'%' identified by 'test_user';
Query OK, 0 rows affected (0.00 sec)

使用 localhost 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -hlocalhost
========= 省略 ===========

mysql> status
/usr/local/mysql57/bin/mysql Ver 14.14 Distrib 5.7.21, for linux-glibc2.12 (x86_64) using EditLine wrapper

Connection id: 9
Current database:
Current user: test_user@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.21-log MySQL Community Server (GPL)
Protocol version: 10
Connection: Localhost via UNIX socket
....

使用 IP 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -h127.0.0.1
Enter password:
========= 省略 ===========

mysql> status
--------------
/usr/local/mysql57/bin/mysql Ver 14.14 Distrib 5.7.21, for linux-glibc2.12 (x86_64) using EditLine wrapper

Connection id: 11
Current database:
Current user: test_user@127.0.0.1
SSL: Cipher in use is DHE-RSA-AES256-SHA
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.21-log MySQL Community Server (GPL)
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP
Server characterset: utf8
...

結果顯示5.7版本的MySQL, % 包括localhost

3.3 MySQL 5.6

創建用戶

db83-3306>>select version();
+------------+
| version() |
+------------+
| 5.6.10-log |
+------------+
1 row in set (0.00 sec)

db83-3306>>create user test_user@'%' identified by 'test_user';
Query OK, 0 rows affected (0.00 sec)

使用 localhost 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -hlocalhost
Enter password:
ERROR 1045 (28000): Access denied for user 'test_user'@'localhost' (using password: YES)

使用 IP 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mysql57/bin/mysql -utest_user -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.10-log MySQL Community Server (GPL)
========= 省略 ===========

mysql> status
--------------
/usr/local/mysql57/bin/mysql Ver 14.14 Distrib 5.7.21, for linux-glibc2.12 (x86_64) using EditLine wrapper

Connection id: 3
Current database:
Current user: test_user@127.0.0.1
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.6.10-log MySQL Community Server (GPL)
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP
......
--------------

結果顯示MySQL 5.6的%不包括localhost

3.4 MySQL 5.1

創建用戶

mysql> select version();
+-----------+
| version() |
+-----------+
| 5.1.73 |
+-----------+
1 row in set (0.00 sec)

mysql> create user test_user@'%' identified by 'test_user';
Query OK, 0 rows affected (0.00 sec)

使用 localhost 登錄

[root@chengqm ~]# mysql -utest_user -p
Enter password:
ERROR 1045 (28000): Access denied for user 'test_user'@'localhost' (using password: YES)
使用 IP 登錄
[root@chengqm ~]# mysql -utest_user -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4901339
Server version: 5.1.73 Source distribution
========= 省略 ===========

mysql> status
--------------
mysql Ver 14.14 Distrib 5.1.73, for redhat-linux-gnu (x86_64) using readline 5.1

Connection id: 4901339
Current database:
Current user: test_user@127.0.0.1
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.1.73 Source distribution
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP

結果顯示 5.1 版本的%不包括localhost

3.5 MariaDB 10.3

創建用戶

db83-3306>>select version();
+---------------------+
| version() |
+---------------------+
| 10.3.11-MariaDB-log |
+---------------------+
1 row in set (0.000 sec)

db83-3306>>create user test_user@'%' identified by 'test_user';
Query OK, 0 rows affected (0.001 sec)

使用 localhost 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mariadb/bin/mysql -utest_user -p -hlocalhost
Enter password:
ERROR 1045 (28000): Access denied for user 'test_user'@'localhost' (using password: YES)

使用 IP 登錄

[mysql@mysql-test-83 ~]$ /usr/local/mariadb/bin/mysql -utest_user -p -h127.0.0.1
Enter password:
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 12
Server version: 10.3.11-MariaDB-log MariaDB Server
========= 省略 ===========

MariaDB [(none)]> status
--------------
/usr/local/mariadb/bin/mysql Ver 15.1 Distrib 10.3.11-MariaDB, for Linux (x86_64) using readline 5.1

Connection id: 12
Current database:
Current user: test_user@127.0.0.1
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server: MariaDB
Server version: 10.3.11-MariaDB-log MariaDB Server
Protocol version: 10
Connection: 127.0.0.1 via TCP/IP

結果顯示MariaDB 10.3的%不包括localhost

4 結論