#!/usr/bin/perl
use 5.010;
use warnings;
use strict;
use DBI;

my $table = 'null_value_table';


open my $fh, '>', $table or die $!;
while ( my $row = <DATA> ) {
    print $fh $row;
}
close $fh or die $!;



my $dbh = DBI->connect( "DBI:CSV:" );
my $sth;


say "\nselect all\n";
$sth = $dbh->prepare( "SELECT * FROM $table" );
$sth->execute();
while ( my @row = $sth->fetchrow_array ) {
    say "@row";
}


say "\n\n\nselect where col1 = Y\n";
$sth = $dbh->prepare( "SELECT * FROM $table WHERE col1 = 'Y'" );
$sth->execute();
while ( my @row = $sth->fetchrow_array ) {
    say "@row";
}


say "\n\n\nselect where col1 <> Y\n";
$sth = $dbh->prepare( "SELECT * FROM $table WHERE col1 <> 'Y'" );
$sth->execute();
while ( my @row = $sth->fetchrow_array ) {
    say "@row";
}


$dbh->disconnect;

__DATA__
col0,col1
1,Y
2,N
3,NULL
4,undef
5,0
6,''
7,