There is this question which has the tag mysqlf
As i can't figure out what mysqlf
can be, in my opinion it is only a typo and should be as such removed.
The linked question is also the only one that has that tag
You could just edit that tag to be [mysql] and since it is the only question with that tag, the tag will eventually be deleted by the system automatically.
See I accidentally created a tag. How do I delete it? (duplicate) for details.