variable escaping ins sql.conf

[Norbert Wegener]

in sql.conf I use something like:

usergroup.GroupName  like 'v%y'

and radius -AX tells me:
WARNING: Unknown variable '%y': See 'doc/variables.txt'

How would I escape that kind of variable to pass it to the sql query?
The usual \ did not work.

Thanks
Norbert Wegener