只显示循环中的一组数据

我相信造成这个问题的原因是我设置的动态WHERE子句。以下是动态WHERE子句的工作原理：

• q.SessionId = ?的强制WHERE条件
• 如果用户从学生下拉菜单中选择单个学生，则将AND sa.StudentId = ?添加到WHERE子句
• 如果用户从学生下拉菜单中选择All学生选项，则从WHERE子句中删除或不显示AND sa.StudentId = ?
• 如果用户从问题下拉菜单中选择单个问题，则将AND q.QuestionId = ?添加到WHERE子句
• 如果用户从问题下拉菜单中选择All问题选项，则从WHERE子句中删除或不显示AND q.QuestionId = ?

我有三个下拉菜单（下面是样本数据的样子）：

会话：

<select name="session" id="sessionsDrop">
<option value="26">POKUB1</option>
<option value="27">POKUB2</option>
</select>

学生：

<select name="student" id="studentsDrop">
<option value="0">All</option>
<option value="39">Luke Mcfadzen</option>
<option value="40">Chris Tucker</option>
</select>

问题：

<select name="question" id="questionsDrop">
<option value="0">All</option>
<option value="72">1</option>
<option value="73">2</option>
</select>

不要忘记我在上面的问题中提到的WHERE条件是如何工作的。假设从会话下拉菜单中选择的会话是POKUB 1, drop down value: 26。

如果你选择了一个学生和一个问题，那么它会正确显示详细信息，例如

• 学生：卢克·麦克法岑-下降值：39
• 问题：1-下拉值：72

所以WHERE条件是q.SessionId = 26 AND sa.StudentId = 39 AND q.QuestionId = 72。

但是，如果我在学生和问题下拉菜单中选择一个或两个All选项，那么输出只显示一个学生和一个问题，出于某种奇怪的原因，它将所有问题的答案组合在一起，并将所有学生的答案组合到一个输出中。

现在，两个下拉菜单中的All选项的下拉值都是0，现在0不是从数据库中选择的值，但我们在dynamicwhere子句中指出，如果从特定的下拉菜单中选择了0值，则从where子句中删除相关条件，例如：

• All学生与单项问题（值72）-WHERE q.SessionId = 26 AND q.QuestionId = 72
• 单个（值39）学生和All问题-WHERE q.SessionId = 26 AND sa.StudentId = 39
• All学生和All问题-WHERE q.SessionId = 26

上述场景存在问题

如果我只是将静态WHERE子句WHERE q.SessionId = ?留给查询，那么如果我选择All students和All Questions，它将正确输出详细信息，但我需要该查询适用于从下拉菜单中选择的所有不同的可能选项，因此我需要动态WHERE子句。我如何才能让它工作，以便输出正确的详细信息？

代码：

    $selectedstudentanswerqry = "
        SELECT
        sa.StudentId, StudentAlias, StudentForename, StudentSurname, q.SessionId, 
        q.QuestionId, QuestionNo, QuestionContent, o.OptionType, q.NoofAnswers, 
        GROUP_CONCAT( DISTINCT Answer ORDER BY Answer SEPARATOR ',' ) AS Answer, r.ReplyType, QuestionMarks, 
        GROUP_CONCAT(DISTINCT StudentAnswer ORDER BY StudentAnswer SEPARATOR ',') AS StudentAnswer, ResponseTime, MouseClick, 
        (
        SELECT sum( StudentMark )
        FROM Student_Answer sta
        WHERE sa.StudentId = sta.StudentId
        AND sa.QuestionId = sta.QuestionId
        )StudentMark
        FROM Student st
        INNER JOIN Student_Answer sa ON (st.StudentId = sa.StudentId)
        INNER JOIN Student_Response sr ON (sa.StudentId = sr.StudentId) AND sa.QuestionId = sr.QuestionId
        INNER JOIN Question q ON (sa.QuestionId = q.QuestionId)
        INNER JOIN Answer an ON q.QuestionId = an.QuestionId
        LEFT JOIN Reply r ON q.ReplyId = r.ReplyId
        LEFT JOIN Option_Table o ON q.OptionId = o.OptionId
        ";
        // 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, QuestionNo
        ";
    // get result and assign variables (prefix with db)
    $selectedstudentanswerstmt->execute(); 
    $selectedstudentanswerstmt->bind_result($detailsStudentId,$detailsStudentAlias,$detailsStudentForename,$detailsStudentSurname,$detailsSessionId,
    $detailsQuestionId,$detailsQuestionNo,$detailsQuestionContent,$detailsOptionType,$detailsNoofAnswers,$detailsAnswer,$detailsReplyType,$detailsQuestionMarks,
    $detailsStudentAnswer,$detailsResponseTime,$detailsMouseClick,$detailsStudentMark); 
    $selectedstudentanswerstmt->store_result();
    $selectedstudentanswernum = $selectedstudentanswerstmt->num_rows(); 
 while ($selectedstudentanswerstmt->fetch()) {
                //Check if the student data exist.
                if (!isset($questions[$detailsStudentId])) {
                    $questions[$detailsStudentId] = array(
                        'studentalias' => $detailsStudentAlias,
                        'studentforename' => $detailsStudentForename,
                        'studentsurname' => $detailsStudentSurname,
                        'questions' => array()
                    );
                }
                $questions[$detailsStudentId]['questions'][$detailsQuestionId] = array(
                    'questionno'=>$detailsQuestionNo,
                    'content'=>$detailsQuestionContent,
                    'optiontype'=>$detailsOptionType,
                    'noofanswers'=>$detailsNoofAnswers,
                    'answer'=>$detailsAnswer,
                    'replytype'=>$detailsReplyType,
                    'questionmarks'=>$detailsQuestionMarks,
                    'studentanswer'=>$detailsStudentAnswer,
                    'responsetime'=>$detailsResponseTime,
                    'mouseclick'=>$detailsMouseClick,
                    'studentmark'=>$detailsStudentMark
                );
            }
            $selectedstudentanswerstmt->close();
    foreach ($questions as $studentId => $studentData) {
        echo '<p>'.$studentData['studentalias'].' - '.$studentData['studentforename'].' '.$studentData['studentsurname'].'</p>';
        foreach ($studentData['questions'] as $questionId => $questionData) {
            echo '<p><strong>'.$questionData['questionno'].': '.$questionData['content'].'<br/>';
            echo $questionData['optiontype'].' - '.$questionData['noofanswers'].' - '.$questionData['answer'].' - '.$questionData['replytype'].' - '.$questionData['questionmarks'].'<br/>';
            echo $questionData['studentanswer'].' - '.$questionData['responsetime'].' - '.$questionData['mouseclick'].' - '.$questionData['studentmark'].'</strong></p>';
        }
    }

以下是$_POST['student']和$_POST['question']的可能var_dump:

单个学生和单个问题：

• 学生：Chris Tucker-字符串（2）"40"
• 问题：1-string（2）"72"

单身学生和所有问题：

• 学生：Chris Tucker-字符串（2）"40"
• 问题：全部字符串（1）"0"

所有学生和单个问题：

• 学生：全部字符串（1）"0"
• 问题：1-string（1）"72"

所有学生和所有问题：

• 学生：全部字符串（1）"0"
• 问题：全部字符串（1）"0"

下面是示例var_dump($questions);，如果我选择All学生和All问题：

array(1) { 
[39]=> array(4) { 
["studentalias"]=> string(8) "u4838229" 
["studentforename"]=> string(5) "Chris" 
["studentsurname"]=> string(6) "Tucker" 
["questions"]=> array(1) { 
[72]=> array(11) { 
["questionno"]=> int(1) 
["content"]=> string(14) "What is a RAM?" 
["optiontype"]=> string(3) "A-E" 
["noofanswers"]=> int(1) 
["answerswer"]=> string(7) "B,C,D,E" 
["replytype"]=> string(6) "Single" 
["questionmarks"]=> int(5) 
["studentanswer"]=> string(9) "A,B,C,D,E" 
["responsetime"]=> string(8) "00:00:07" 
["mouseclick"]=> int(1) 
["studentmark"]=> string(1) "2" } } } }