MySQL Logger Extension (Free)
This module will log all sql queries to your system/storage/log directory as file sql.log so you can see all the sql queries executed by Opencart.
Video below shows how it works.
Once you have installed the extension you will need to FTP into you server and go into you /system/storage/log folder and open/download the sql.log file which contains all SQL's executed since been installed. Remember to disable the extension when don't use it so don't create massive log files.