my $dbh = DBI->connect(@params);
my $gen = SQL::Abstract->new;
my ($insert, @bind) = $gen->insert(atable=>{a=>undef,b=>1,c=>'string'});
my $sth = $dbh->prepare($insert);
$sth->execute(@bind);
__END__
$insert eq "INSERT INTO atable ( a, b, c) VALUES ( ?, ?, ? )"
@bind contains undef, 1, "string"