my Mysql DBD insert call suddently silently fails - perl

Question

use DBI();
What is causing this insert to fail to err 1, the SELECT call works OK so its not credential issue.
$dbh = DBI->connect("DBI:mysql:$dbname:$dbhost","$dbuser","$dbpass");
my $sth = $dbh->prepare( "INSERT INTO call_fields VALUES ( ?, ?, ?, ? )" ) or die print "$DBI:errstr";
$sth->execute( "NULL", 0, 0, "testing" ) or die print "er $DBI::errstr";
mysql ver 5.5
This is perl 5, version 14, subversion 1 (v5.14.1) built for MSWin32-x64
NOTE: This syntax works OK:
$dbh->do(q/insert into call_fields values(null,0,0,"testing") /) or die "$dbh::errstr";

Answer 1

Set the RaiseError connection attribute and let DBI do the error handling.
The SQL NULL value is represented as undef in Perl, not the quoted string NULL.
use strictures;
use DBI qw();
my $dbh = DBI->connect("DBI:mysql:$dbname:$dbhost", $dbuser, $dbpass, { RaiseError => 1 });
my $sth = $dbh->prepare('INSERT INTO call_fields VALUES ( ?, ?, ?, ? )');
$sth->execute(undef, 0, 0, 'testing');

Answer 2

The statement
die print "$DBI:errstr";
is suspect. As Alan Haggai Alavi pointed out in the comments, you are missing a colon. It should be $DBI::errstr. Also, it is displaying 1 in stdERR (not stdout) because you chain die with print. print returns 1 for a successful print, which is returned to die and then displayed.
It should also display the print -- in stdout -- or at least a warning of undefined value in print, but unless you are using use warnings, it will be rather silent. (It might print :errstr.)
So:
die $DBI::errstr;
Should improve your situation. Adding
use strict;
use warnings;
if it is not already there will further improve it.

Answer 3

In the hope that you're just a little confused trying to collate all the information that you've been given, here is your code rewritten to use all of the suggestions you've been given (along with a couple of other changes that I've made).
I've commented the changes I've made on each line.
# Declared $dbh
# Removed unnecessary quote marks.
my $dbh = DBI->connect("DBI:mysql:$dbname:$dbhost", $dbuser, $dbpass);
# Removed unnecessary call to print
# Replaced $DBI::errstr with $sth->errstr
my $sth = $dbh->prepare( 'INSERT INTO call_fields VALUES ( ?, ?, ?, ? )' )
or die $sth->errstr;
# Replaced string "NULL" with undef (which DBI treats as NULL)
# Removed unnecessary call to print
# Replaced $DBI::errstr with $sth->errstr
$sth->execute( undef, 0, 0, 'testing' ) or die $sth->errstr;
I suspect it's the removal of the unnecessary print calls and switching "NULL" to undef that actually fix your problem.
In addition, I'd strongly recommend a) setting the RaiseError flag when connecting to the DB and b) adding the column names to the INSERT statement and then removing the first, nullable, column from the statement completely.

Answer 4

Your error printing:
... or die print "er $DBI::errstr";
doesn't look right.
As Alan mentioned, you fixed the double colon, but the call to print that die is executing is returning 1. (1 == successful print...somewhere)
Change your die syntax to this:
... or die "er $DBI::errstr";
You should get something like this:
er {DBI_ERROR_MESSAGE} at {Script_Name} line XXX.
You wrote:
$dbh = DBI->connect("DBI:mysql:$dbname:$dbhost","$dbuser","$dbpass");
my $sth = $dbh->prepare( "INSERT INTO call_fields VALUES ( ?, ?, ?, ? )" ) or die print "$DBI:errstr";
$sth->execute( "NULL", 0, 0, "testing" ) or die print "er $DBI::errstr";
and another example:
$dbh->do(q/insert into call_fields values(null,0,0,"testing") /) or die "$dbh::errstr";
This is an "apples and oranges" comparison. The first one is doing an insert of the string "NULL", but the second one is inserting the 'null' value.
I assume your call_fields table that is getting the first prepared input value is not accepting strings, and thus the $sth->execute is failing.