ON DUPLICATE KEY仍然複製插入

我有一個問題，不是檢查是否有重複，而是下面的腳本只是將行插入到mysql中，根本沒有更新。我試過一遍又一遍，但總是有重複。ON DUPLICATE KEY仍然複製插入

我究竟在做什麼錯在這裏？

if ($completeStatus == "0") { 

// Get the default questions responses and insert into database 
$questionsAnswered = $_GET['questions']; 
foreach($questionsAnswered as $key => $answers){ 
    $query = "INSERT INTO survey_ResponseDetail (responseHeader, 
         questionID, 
         questionText, 
         ansLikelihood, 
         ansExpConsq, 
         ansRepRisk, 
         currWayMitigate 
        ) 
VALUES ('$ResponseHeader', 
     '$key', 
     'test1', 
     '$answers[1]', 
     '$answers[2]', 
     '$answers[3]', 
     '$answers[4]' 
     ) 
ON DUPLICATE KEY UPDATE ansLikelihood = '$answers[1]', 
         ansExpConsq = '$answers[2]', 
         ansRepRisk = '$answers[3]', 
         currWayMitigate = '$answers[4]', 
         id = LAST_INSERT_ID(id)"; 
    $dbresult = mysql_query($query) or die ('Database Error (' . mysql_errno() . ') ' . mysql_error()); 

}

來源

2012-06-19 Keiran Lovett

不得不問。您在survey_ResponseDetail表上確實有PK或其他唯一約束。對？ – JohnFx

我對mySQL的知識現在非常弱，所以我不知道。如果我在創建表格時必須設置它，那麼不需要。 –