my $sql = "SELECT * FROM mytable WHERE foo = bar";
my $sth = $dbh->prepare($sql);
$sth->execute() || die $DBI::errstr;

my $row = $sth->fetchrow_hashref;
my %cols = %$row;

# Print the field names
print join(', ', sort keys %cols);

# Print corresponding values
print join(', ', map { defined $cols{$_} ? $dbh->quote($cols{$_}) : 'NULL' } sort keys %cols);