I agree that if you can, SELECT COUNT(name) WHERE ...
works best. Also, depending on whether or not the NAME column is a primary key or otherwise unique value, you may want SELECT COUNT (DISTINCT name) WHERE ...
to get a count of all the guaranteed unique names.
But if for some reason you can't or you don't want to, you can use this snippet after your original query:
my $rows = $sth->fetchall_arrayref()
my $num_rows = scalar (@$rows);
It will return a reference to an AoA (Array of Arrays). The scalar
is optional, of course.
You can then use the data in $rows for actual manipulation, if the need arises...