SQL 錯誤訊息輸出

今天為了實做資料的輸入驗證,嚐試了在SQL中許多調整.
設定column的primary key(避免column重複),並利用perl dbi模組的錯誤輸出顯示出重複資料的判斷:

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##以下為建立與mysql資料庫連結
$dbh = DBI->connect('dbi:mysql:test;host=127.0.0.1;port=3306', $username , $pwd , {PrintError =>0}) ;
die "unable connect : $dbi::errstr \n" unless (defined $dbh);

$sth = $dbh->prepare("insert into special_cm_config(customer_no,customer_ip,customer_mac,description,type) values(?,?,?,?,?)") or die "Cannot prepare: " . $dbh->errstr();
$sth->execute($customer_no,$customer_ip,$customer_mac,$description,$type);
if($sth->err()){
print "已有重複的客戶編號,錯誤訊息:". $dbh->errstr()."\n";
exit();};
$dbh->disconnect ;