I found a solution, namely:

sub {
my $tags = shift;
my $ed_db = $DB->table('Editors', 'Users');
my $user = $tags->{Username};
my $sth = $ed_db->select ( { 'Editors.Username' => $user } );
my $editor_info = $sth->fetchrow_hashref;
return $editor_info;
}

I forgot the: my $user = $tags->{Username};

but how can I set the names of the categories, in which the user are editor, and the links they own???
I have to make a combination with the category & linkstable, but how????