There are two ways to do this, one being using phpMyAdmin the other is via SSH.
Using phpMyAdmin:- Login to your control panel at www.yourdomain.com/cpanel
- Click on 'phpMyAdmin' under the 'Databases' menu
- From the dropdown list to the left, choose the database you wish to export the backup from.
- Click on the 'Export' Tab.
- Click to deselect the 'Data 'box, then tick the 'Save as file' box and 'Go'.
- You will be asked to save the .sql file to the hard drive, click 'Save'.
- Choose the location to save to and click 'Save'.
The command line option from SSH is:
mysql -d -p database_name > file.sql
Where 'database_name' is the name of your database, and 'file.sql' is the name of the file you would like to write the table structure to. You will be prompted you for a password (-p). Normally mysqldump gives you the entire database, with the '-d' option, you need to tell it to not include the data, just the table structure.