Question

我在下面的查询中有一个动态where子句，它根据所选的下拉菜单输出结果。现在，where子句在添加和删除某些条件时可以正常工作，具体取决于所选的选项。

但我有点意识到，如果我想查看所有问题，它没有QuestionId = ?条件，这是好的，但是当假设显示每个问题的答案时，而不是像这样显示：

D (this is for question 1)
B,C,E (this is for question 2)

将它们全部显示为如下所示的一个答案：

D,B,C,E

我的问题是导致这个，查询或循环的原因是什么？

var_dump（$ questions）：显示：

array(1) { [39]=> array(1) { [72]=> array(1) { ["answer"]=> string(7) "B,C,D,E" } } }

72是QuestionId，所以出于一些奇怪的原因，它没有经过所有问题（应该有第二个问题是73）

以下是代码：

    $selectedstudentanswerqry = "
            SELECT sa.StudentId, q.QuestionId,
            GROUP_CONCAT( DISTINCT Answer ORDER BY Answer SEPARATOR ',' ) AS Answer
            FROM Student st
            INNER JOIN Student_Answer sa ON (st.StudentId = sa.StudentId)
            INNER JOIN Question q ON (sa.QuestionId = q.QuestionId)
            INNER JOIN Answer an ON q.QuestionId = an.QuestionId
            ";

            // Initially empty
            $where = array('q.SessionId = ?');
            $parameters = array($_POST["session"]);
            $parameterTypes = 'i';


            //check if POST is empty

            // Check whether a specific student was selected
            $p_student = empty($_POST["student"])?'':$_POST["student"];

            switch($p_student){
            case 0:
                //dont' add where filters
                break;
            default:
                $where[] = 'sa.StudentId = ?';
                $parameters[] .= $_POST["student"];
                $parameterTypes .= 'i';
            }

            // Check whether a specific question was selected
            $p_question = empty($_POST["question"])?'':$_POST["question"];

            switch($p_question){
            case 0:
                //dont' add where filters
                break;
            default:
                $where[] = 'q.QuestionId = ?';
                $parameters[] .= $_POST["question"];
                $parameterTypes .= 'i';
            }

            // If we added to $where in any of the conditionals, we need a WHERE clause in
            // our query
            if(!empty($where)) {
                $selectedstudentanswerqry .= ' WHERE ' . implode(' AND ', $where);
                global $mysqli;
                $selectedstudentanswerstmt=$mysqli->prepare($selectedstudentanswerqry);
                // You only need to call bind_param once

                if (count($where) == 1) {
                $selectedstudentanswerstmt->bind_param($parameterTypes, $parameters[0]);
            }
            else if (count($where) == 2) {
                $selectedstudentanswerstmt->bind_param($parameterTypes, $parameters[0], $parameters[1]);
            }
            else if (count($where) == 3) {
                $selectedstudentanswerstmt->bind_param($parameterTypes, $parameters[0], $parameters[1], $parameters[2]);
            }

            }

            $selectedstudentanswerqry .= "
              GROUP BY sa.StudentId, q.QuestionId
              ORDER BY StudentAlias, q.SessionId
            ";

        // get result and assign variables (prefix with db)
        $selectedstudentanswerstmt->execute(); 
        $selectedstudentanswerstmt->bind_result($detailsStudentId,$detailsQuestionId,$detailsAnswer);   

        $selectedstudentanswerstmt->store_result();
        $selectedstudentanswernum = $selectedstudentanswerstmt->num_rows(); 

    $questions = array();

    while ($selectedstudentanswerstmt->fetch()) {

        $questions[$detailsStudentId][$detailsQuestionId] = array(

        'answer'=>$detailsAnswer,

);

}

...

<?php   

var_dump($questions);

        foreach ($questions as $studentId => $student)
{

foreach ($student as $questionId => $question) {

echo '<p><strong>Answer:</strong> ' .htmlspecialchars($question['answer']).  '</p>' . PHP_EOL;

}

}

?>

Answer 1

看起来问题实际上是：

GROUP_CONCAT( DISTINCT Answer ORDER BY Answer SEPARATOR ',' ) AS Answer

查询的一部分。如果没有看到实际的表结构和数据，就很难形成正在发生的事情的心理形象。 “答案”可能是一个模糊的列，因此会导致不可预测的结果。

您可以考虑编写子查询或为此创建视图。

SELECT sa.StudentID, q.QuestionId, sa.Student_Answers
FROM (
     SELECT GROUP_CONCAT(DISTINCT a.Answer SEPERATOR ',') as Question_Answers
     FROM Student_Answer a
     GROUP BY a.QuestionID
) AS sa
INNER JOIN Question q ON (sa.QuestionId = q.QuestionId)

查看您的代码，似乎没有必要加入Students表，因为他们的答案中已经存在ID。虽然我确信在某些时候你会将名字与ID相关联。

它没有正确循环答案？

1 个答案: