Hi,
Yes, via phpMyAdmin everything can be done.
But be careful, the best way will be to create 2 or 3 entries, then export it to see how the entries are in the database, then create your import file, you can let the category_left and category_right entries empty and then once entries added, click on the "Rebuild" button in the toolbar of the categories listing page.
Before anything, please backup. The safest way is still to add them manually, it will take 30 minutes but you are sure that the entries will be correct