解决方法：
先导出为txt文件，其内容是以逗号“，”分隔的，得到txt文件后，再自行处理为.csv或者.xls文件。
参数说明：
-t, --no-create-info Don't write table creation info.
-T, --tab=name Create tab-separated textfile for each table to given path. (Create .sql and .txt files.) NOTE: This only works if mysqldump is run on the same machine as the mysqld server.
--fields-terminated-by=name Fields in the output file are terminated by the given string.
--fields-enclosed-by=name Fields in the output file are enclosed by the given character.
1. 先查看可导出位置（不然会涉及到权限问题）
mysql> show variables like 'secure_file_priv';
+------------------+-----------------------+
| Variable_name | Value |
+------------------+-----------------------+
| secure_file_priv | /var/lib/mysql-files/ | //如果出现权限问题，尝试把该目录所有者改成mysql
+------------------+-----------------------+
row in set (0.00 sec)
2. 执行导出命令
[root@server-10 ~]# mysqldump -uroot -p -t -T /var/lib/mysql-files/ mydb customers --fields-terminated-by=',' --fields-enclosed-by='\"'
3. 查看一下
[root@server- ~]# ls -l /var/lib/mysql-files/
total
-rw-r--r-- root root Aug : customers.sql //会同步生成同名sql文件，内容为空
-rw-rw-rw- mysql mysql Aug : customers.txt
[root@server- ~]# cat /var/lib/mysql-files/customers.txt
"","Coyote Inc.","200 Maple Lane","Detroit","MI","","USA","Y Lee","ylee@coyote.com"
"","Mouse House","333 Fromage Lane","Columbus","OH","","USA","Jerry Mouse",\N
"","Wascals","1 Sunny Place","Muncie","IN","","USA","Jim Jones","rabbit@wascally.com"
"","Yosemite Place","829 Riverside Drive","Phoenix","AZ","","USA","Y Sam","sam@yosemite.com"
"","E Fudd","4545 53rd Street","Chicago","IL","","USA","E Fudd",\N
4. 如果不想每个字段带冒号，则省略--fields-enclosed-by='\"'即可
[root@server- ~]# mysqldump -uroot -p -t -T /var/lib/mysql-files/ mydb customers --fields-terminated-by=','
5. 再查看一下输出的变化
[root@server- ~]# ls -l /var/lib/mysql-files/
total
-rw-r--r-- root root Aug : customers.sql
-rw-rw-rw- mysql mysql Aug : customers.txt
[root@server- ~]# cat /var/lib/mysql-files/customers.txt
,Coyote Inc., Maple Lane,Detroit,MI,,USA,Y Lee,ylee@coyote.com
,Mouse House, Fromage Lane,Columbus,OH,,USA,Jerry Mouse,\N
,Wascals, Sunny Place,Muncie,IN,,USA,Jim Jones,rabbit@wascally.com
,Yosemite Place, Riverside Drive,Phoenix,AZ,,USA,Y Sam,sam@yosemite.com
,E Fudd, 53rd Street,Chicago,IL,,USA,E Fudd,\N
结束.