MySQL 127.0.0.1和localhost本质区别

登录方式：

[root@10-4-14-168 ~]# mysql -uroot -p
Enter password:

查看权限表

mysql> SELECT user,host,password FROM mysql.user;
+------+-------------+-------------------------------------------+
| user | host        | password                                  |
+------+-------------+-------------------------------------------+
| root | localhost   | *11B9ACA21786F766739D0EB1483C5F64212B81AC |
| root | 10.4.14.168 | *11B9ACA21786F766739D0EB1483C5F64212B81AC |
| root | 127.0.0.1   | *11B9ACA21786F766739D0EB1483C5F64212B81AC |
| root | ::1         | *11B9ACA21786F766739D0EB1483C5F64212B81AC |
+------+-------------+-------------------------------------------+
4 rows in set (0.00 sec)

查看当前的IP地址：

inet addr:10.4.14.168

　　

验证一下三种登陆方式：

# mysql -h localhost -uroot -p
可以登陆

mysql> status;
--------------
mysql  Ver 14.14 Distrib 5.5.39, for Linux (x86_64) using readline 5.1

Connection id:          6
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    utf8
Conn.  characterset:    utf8
UNIX socket:            /var/lib/mysql/mysql.sock
Uptime:                 19 min 8 sec

Threads: 1  Questions: 24  Slow queries: 0  Opens: 33  Flush tables: 1  Open tables: 26  Queries per second avg: 0.020
--------------

　　

# mysql -h 127.0.0.1 -uroot -p 

mysql> status;
--------------
mysql  Ver 14.14 Distrib 5.5.39, for Linux (x86_64) using readline 5.1

Connection id:          4
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp
Protocol version:       10
Connection:             127.0.0.1 via TCP/IP
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:               3306
Uptime:                 2 min 24 sec

Threads: 2  Questions: 21  Slow queries: 0  Opens: 33  Flush tables: 1  Open tables: 26  Queries per second avg: 0.145
--------------

　　

# mysql -h 10.4.14.168 -uroot -p

mysql> status;
--------------
mysql  Ver 14.14 Distrib 5.5.39, for Linux (x86_64) using readline 5.1

Connection id:          5
Current database:
Current user:           root@10-4-14-168
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp
Protocol version:       10
Connection:             10.4.14.168 via TCP/IP
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:               3306
Uptime:                 3 min 9 sec

Threads: 2  Questions: 30  Slow queries: 0  Opens: 33  Flush tables: 1  Open tables: 26  Queries per second avg: 0.158
--------------

　　

# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 7
Server version: 5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> status;
--------------
mysql Ver 14.14 Distrib 5.5.39, for Linux (x86_64) using readline 5.1

Connection id: 7
Current database:
Current user: root@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: latin1
Db characterset: latin1
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /var/lib/mysql/mysql.sock
Uptime: 22 min 31 sec

Threads: 1 Questions: 31 Slow queries: 0 Opens: 33 Flush tables: 1 Open tables: 26 Queries per second avg: 0.022
--------------

　　

下面尝试修改下host域

mysql> select user,host from mysql.user;
+------+-------------+
| user | host        |
+------+-------------+
| root | 10.4.14.168 |
| root | 127.0.0.1   |
| root | ::1         |
| root | localhost   |
+------+-------------+
4 rows in set (0.00 sec)

mysql> UPDATE mysql.user SET host ='10.4.5.9' WHERE host ='::1';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT user,host FROM mysql.user;
+------+-------------+
| user | host        |
+------+-------------+
| root | 10.4.14.168 |
| root | 10.4.5.9    |
| root | 127.0.0.1   |
| root | localhost   |
+------+-------------+
4 rows in set (0.00 sec)

　　

现在如果10.4.5.9这台机器和这台10.4.14.168的连通性没问题的话就可以这种方式登陆：

inet addr:10.4.5.9

[root@10-4-5-9 ~]# mysql -h 10.4.14.168 -uroot -P 3306 -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 3
Server version: 5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> 

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

Connection id:          3
Current database:
Current user:           root@10.4.5.9
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         5.5.39-cll-lve MySQL Community Server (GPL) by Atomicorp
Protocol version:       10
Connection:             10.4.14.168 via TCP/IP
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    latin1
Conn.  characterset:    latin1
TCP port:               3306
Uptime:                 1 min 13 sec

Threads: 2  Questions: 14  Slow queries: 0  Opens: 33  Flush tables: 1  Open tables: 26  Queries per second avg: 0.191
--------------

　　

由此：引出了user表中host列的IP地址和localhost的区别：

IP地址：-h  IP   是通过TCP/IP连接方式连接的。

localhost ：-h  localhost 或者 直接忽略-h  是通过socket连接方式连接的。

一般远程连接或者PHP、C等连接MySQL的时候都要指定IP地址，通过TCP/IP 方式连接

可以通过修改配置文件my.cnf

protocol=tcp  强制使用TCP/IP 连接

skip-networking  强制使用socket来连接。