PHP RIGHT JOIN查詢不考慮null？

當我運行查詢時，它返回所有正確的值，除了它不返回任何值，其中a.Correct = null（即一個測驗問題根本沒有被回答），但它確實返回值爲a.Correct = 0PHP RIGHT JOIN查詢不考慮null？

/***Configure the retest***/ 
    public function CreateRetest($topicID) { 
    $retestData = array(); 
    $count = 0; 

    $createSQL = "SELECT q.QuestionID,q.Question,q.Answer,q.TopicID From quizanswered a RIGHT JOIN question q ON a.QuestionID = q.QuestionID where (a.Correct=null OR a.Correct = 0) AND q.TopicID = '$topicID'"; 
    $create = mysqli_query($this->db,$createSQL) or die(mysqli_connect_errno()."Cannot create tables"); 
    while($row = mysqli_fetch_array($create)){ 
    $rQuestionID = $row['QuestionID']; 
    $rQuestion = $row['Question']; 
    $rAnswer = $row['Answer']; 
    $retestData[$count] = array($rQuestionID,$rQuestion,$rAnswer); 
    $count +=1; 
    } 
    return $retestData; 

}

來源

2016-12-07 Kurt Görg

你的問題是不相關的PHP。刪除PHP標籤和所有的PHP代碼，並保持**只有** SQL查詢 – Dekel

更換=null與IS NULL

SELECT 
    q.QuestionID, 
    q.Question, 
    q.Answer, 
    q.TopicID 
FROM quizanswered a 
RIGHT JOIN question q 
ON a.QuestionID = q.QuestionID 
WHERE (a.Correct IS NULL OR a.Correct = 0) AND q.TopicID = '$topicID'

來源

2016-12-07 02:24:03

PHP RIGHT JOIN查詢不考慮null？

回答

相關問題