对于web应用来说，经常会用到mysql，而数据的备份与还原是web应用经常做的事，一般来说，用客户端工具phpmyadmin，sqlyog 等，来备份数据库没有任何问题，还原时经常碰到mysql提示的#2006错误。
2006 (<code class="literal">CR_SERVER_GONE_ERROR)Message: MySQL server has gone away
原因可能是sql语句过长，超过mysql通信缓存区最大长度；
调整mysql配置文件中max_allowed_packet
# Example MySQL config file for medium systems. # # This is for a system with little memory (32M - 64M) where MySQL plays # an important part, or systems up to 128M where MySQL is used together with # other programs (such as a web server) # # You can copy this file to # /etc/my.cnf to set global options, # mysql-data-dir/my.cnf to set server-specific options (in this # installation this directory is C:\mysql\data) or # ~/.my.cnf to set user-specific options. # # In this file, you can use all long options that a program supports. # If you want to know which options a program supports, run the program # with the "--help" option. # The following options will be passed to all MySQL clients [client] #password = your_password port = 3306 socket = /tmp/mysql.sock # Here follows entries for some specific programs # The MySQL server [wampmysqld] #mysql端口 port = 3306 socket = /tmp/mysql.sock #索引缓存区，决定你索引查询时能访问速度 key_buffer_size = 16M #通信缓存区最大长度，决定你sql语句中字符串最大长度 max_allowed_packet = 1M #排序缓存区，决定你orderby的速度 sort_buffer_size = 512K #通信缓存区大小，查询时默认该值为通信缓存区大小，若不够会自动增加直到达到max_allowed_packe net_buffer_length = 8K read_buffer_size = 256K read_rnd_buffer_size = 512K myisam_sort_buffer_size = 8M
