#查看某个表的结构（当前数据库mysql，查看表user）：
mysql > desc user;
mysql > describe user;
mysql > show columns from user;
mysql > show fields from user;
mysql > show create table user;
mysql > select * from information_schema.columns where table_schema='mysql' and table_name='user';


----------------------------------------------------
mysqldump 备份数据
----------------------------------------------------
#导结构不导数据 
> mysqldump -u root -p --opt -d 数据库名 > xxxx.sql
#栗子：
> mysqldump -u root -p --opt -d mysql > /home/kk/mysql.sql

#导数据不导结构 
> mysqldump -u root -p --opt -t 数据库名 > xxxx.sql
#栗子：
> mysqldump -u root -p --opt -t mysql > /home/kk/mysql.sql

#导出数据和结构 
> mysqldump -u root -p 数据库名 > xxxx.sql
#栗子：
> mysqldump -u root -p mysql > /home/kk/mysql.sql

#导出多个数据库（数据和结构 ）
> mysqldump -u root -p -B 数据库A 数据库B 数据库C > xxxx.sql

#导出数据库多个表（数据和结构 ）
> mysqldump -u root -p 数据库A 表A 表B > xxxx.sql
> mysqldump -u root -p 数据库A --tables 表A 表B > xxxx.sql
#栗子：
> mysqldump -u root -p mysql db user func > /home/kk/mysql.sql
> mysqldump -u root -p -B mysql --tables db func > /home/kk/mysql.sql

----------------------------------------------------
mysqldump 还原数据
----------------------------------------------------
# mysqldump -u用户 -p密码 数据库 < /home/kk/mysql.sql
#栗子：
> mysqldump -uroot -p mysql < /home/kk/mysql.sql

# mysql -u用户 -p密码 数据库 < xxxx.sql
#栗子：
> mysql -uroot -p < /home/kk/mysql.sql
> mysql -uroot -p mysql < /home/kk/mysql.sql

# 登录mysql执行
mysql> source /home/kk/mysql.sql;


压缩备份
mysqldump -uroot -p'pwd' -B db1db2 | gzip >/db_back.sql.gz

批量压缩备份
mysqldump -uroot -p'pwd' -e"show databases;" | grep -Eiv "database|infor|perfor" | sed -r 's#^([a-z].*$)#mysqldump -uroot -p 'pwd' --event -B \1|gzip > /opt/back/\1.sql.gz#g'|bash



----------------------------------------------------
outfile 导出数据
http://dev.mysql.com/doc/refman/5.7/en/select-into.html
----------------------------------------------------
mysql> select host, user from mysql.user;

# 导出数据到变量
mysql> select host, user into @x, @y from mysql.user limit 1;
mysql> select @x,@y;

# 导出数据到文件
mysql> select host, user from mysql.user into outfile '/home/kk/file_name.txt';

  #可能错误
  ERROR 1290 (HY000): The MySQL server is running with the --secure-file-priv option so it cannot execute this statement

  解决：
  1. 设置安全目录： vi /etc/my.cnf
  secure-file-priv=/home/kk/

  2. 有权限写入目录/home/kk/


# 详细写法
select host, user 
into outfile '/home/kk/file_name.txt'
fields terminated by ',' 
optionally enclosed by '"'
lines terminated by '\n'
from mysql.user;

select host, user from mysql.user
into outfile '/home/kk/file_name.txt'
fields terminated by ',' 
optionally enclosed by '"'
lines terminated by '\n';


# 其他写法
> mysql -u root -p -e "SELECT host, user FROM mysql.user" > /home/kk/file_name.txt
 
----------------------------------------------------
load data infile 导入数据
http://dev.mysql.com/doc/refman/5.7/en/load-data.html
----------------------------------------------------

mysql> create database test;
mysql> create table test.tab as select host,user from mysql.user where 1=2;

# 导入数据
mysql> load data infile '/home/kk/file_name.txt' into table test.tab;

# 导入数据，忽略第一行（如有标题）
mysql> load data infile '/home/kk/file_name.txt' into table test.tab ignore 1 lines;


# 自定义格式倒入（文本如： "localhost","root"）
load data infile '/home/kk/file_name.txt' 
into table test.tab
fields terminated by ',' 
optionally enclosed by '"'
lines terminated by '\n';