Question

What commands I can use at ssh to export(download) mysql database using SSH?

Answer 1

To export a mysql dump using SSH, execute the following command:

mysqldump -u username -p dbname > db_dump.sql

username -> your mysql username
dbname   -> your database name

Enter password when prompted. And you are done.

Have a look here: MySQL Import and Export (.sql file) via SSH

Hope this helps.