Hi: How can I separate the undef data and NULL data? the following code work ok for undef/null data but Ｉwon't know which one is undef and which is null they all print out " ". 
use strict;
use DBI;
use Data::Dumper;

my $dbh = 
    DBI->connect("dBi:mysql:cacti:localhost",
    "cacti", 
    "cacti") 
    or die("Cannot connect: $DBI::errstr\n");


my $sth = $dbh->prepare("select * from data_template_data");

$sth->execute;



my $names = $sth->{NAME};
for (@$names)
{
    printf("%-10s",$_);
}
print "\n";

while (my $row_ref = $sth->fetch())
{
    for (@$row_ref)
    {
        if (defined($_))
        {
            printf("%-10s",$_);
        }
#        elsif ($_ eq '')
#        {
#            print 'NULL';
#        }
        elsif (undef($_))
        {
            print "\' \'";
        }
    }
    print "\n";
}

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In reply to Perl DBI NULL and undef by chefchanyu

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