Well, if you did it the way I described in the how to then the incremental means only altered files are transferred for backup... however due to the nature of hardlinks you do have full backups at any given time.
A harddisk consists of two parts:
(1) Table of contents
(2) The actual data
When you create a file it will create an entry in the table of contents. That one says where the file is physically located on the hardisk.
When you make a hardlink, you double the toc and copy it to another place. I looks like you will then have twice the files (which consumes only a little more space than the file itself, since only the toc entry was doubled).
So as long as you have somehwere a hardlink pointing to the file then the file does exist.
What now rsync does is compare whether files have changed. If they have, then rsync will remove 1 hardlink (the others still remain and hence also the files) and create a new file... in that case you do have the file double on your disk (but in two different versions).
The correct syntax for restoring mysql dbs is:
mysql - u user_name -p your_password database_name < file_name.sql