MySQL 连接方式
1：TCP/IP 套接字方式
这种方式会在TCP/IP 连接上建立一个基于网络的连接请求，一般是client连接跑在Server上的MySQL实例，2台机器通过一个TCP/IP 网络连接。
C:\Users\gechong>mysql -h
192.168.
1.10 -uroot -p
Enter password: *******
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.5. 20-log MySQL Community Server (GPL)
Copyright (c) 2000, 2011, 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>
Enter password: *******
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.5. 20-log MySQL Community Server (GPL)
Copyright (c) 2000, 2011, 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>
这里的客户端是Windows，向IP为192.168.1.10 的服务器上的MySQL实例发起了TCP/IP请求，连接成功后就可以使用MySQL了。
可以查看：
mysql> SELECT user,host,password FROM mysql.user \G
*************************** 1. row ***************************
user: root
host: localhost
password: *11B9ACA21786F766739D0EB1483C5F64212B81AC
*************************** 2. row ***************************
user: root
host: 127.0. 0.1
password: *11B9ACA21786F766739D0EB1483C5F64212B81AC
*************************** 3. row ***************************
user: gechong
host: localhost
password: *7AE39BE5035D5C32361400FF7DEDD757AA76896A
3 rows in set ( 0.02 sec)
*************************** 1. row ***************************
user: root
host: localhost
password: *11B9ACA21786F766739D0EB1483C5F64212B81AC
*************************** 2. row ***************************
user: root
host: 127.0. 0.1
password: *11B9ACA21786F766739D0EB1483C5F64212B81AC
*************************** 3. row ***************************
user: gechong
host: localhost
password: *7AE39BE5035D5C32361400FF7DEDD757AA76896A
3 rows in set ( 0.02 sec)
这张权限表清楚的显示了MySQL允许哪些用户在哪些IP段内连接
2：UNIX域套接字
UNIX域套接字并不是网络协议，所以只能在MySQL客户端和数据库实例在一台服务器上使用，用户可以在配置文件中指定套接字文件
--socket=/tmp/mysql.sock
mysql> SHOW VARIABLES LIKE ' socket ';
+---------------+-----------------+
| Variable_name | Value |
+---------------+-----------------+
| socket | /tmp/mysql.sock |
+---------------+-----------------+
1 row in set ( 0.00 sec)
#mysql -uroot -S/tmp/mysql.sock