in reply to Handling Null or Undef values in DBI (and things of those nature)...

Or a slightly different syntax:
my ($field1, $field2, $field3) = (undef, undef, undef); my $sth = $dbh->prepare('select * from table'); $sth->execute; if ($sth->rows > 0) { $sth->bind_columns(\($field1, $field2, $field3)); $sth->fetch; } $sth->finish; for ($field1, $field2, $field3) { $_ ||= '' }
When dealing with failures caused by duplicate values (due to a constraint) I just check like this:
$dbh->do('insert into blah (?, ?, ?)', undef, $x, $y, $z); if ($dbh->err) { if ($dbh->err == 1062) { # duplicate } else { # some other problem } }
1062 happens to be the error code for MySQL.

Look at $DBI::lasth->{Statement} which has the last SQL statement you tried to execute which is quite handy in a debug subroutine.