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


my $dbh = DBI->connect( "DBI:CSV:", undef, undef, { RaiseError => 1, csv_null => 1, } ); # csv_null => 0
my $table = 'Table1.csv';
my( $sth, $sql );

sub output {
    my $sql = shift;
    say $sql;
    $sth = $dbh->prepare( $sql );
    $sth->execute();
    while ( my @row = $sth->fetchrow_array ) {
        say DBI::neat_list( \@row )
    }
    say "";
}
 
$dbh->do( "DROP TABLE IF EXISTS $table" );
$dbh->do( "CREATE TABLE $table ( id INT, nachname CHAR(64), vorname CHAR(64) )" );

$sth = $dbh->prepare("INSERT INTO $table( id, nachname, vorname ) VALUES (?,?,?)");

$sth->execute( 1, 'Lohan', 'Lindsay' );
$sth->execute( 2, '', '' );
$sth->execute( 3, undef, undef );


$sql = "SELECT * FROM $table";
output( $sql );
$sql = "SELECT * FROM $table WHERE vorname = 'Lindsay'";
output( $sql );
$sql = "SELECT * FROM $table WHERE vorname <> 'Lindsay'";
output( $sql );

$dbh->disconnect;

SELECT * FROM Table1.csv
'1', 'Lohan', 'Lindsay'
'2', '', ''
'3', '', ''

SELECT * FROM Table1.csv WHERE vorname = 'Lindsay'
'1', 'Lohan', 'Lindsay'

SELECT * FROM Table1.csv WHERE vorname <> 'Lindsay'
'2', '', ''
'3', '', ''

SELECT * FROM Table1.csv
'1', 'Lohan', 'Lindsay'
'2', '', ''
'3', undef, undef

SELECT * FROM Table1.csv WHERE vorname = 'Lindsay'
'1', 'Lohan', 'Lindsay'

SELECT * FROM Table1.csv WHERE vorname <> 'Lindsay'
'2', '', ''

my $nn;
my $vn = Paul;
my $array_ref = [       [ qw( id nachname vorname ) ],  
                        [ 1, 'Lohan', 'Lindsay' ], 
                        [ 2, undef, 'Karl' ],   # gut
                        [ 3, $nn, $vn ],        # auch gut
                        [ 4, ,'Peter' ],        # nicht gut     
];

$dbh->do( "CREATE TEMP TABLE $table AS import( ? )", {}, $array_ref );