仅显示循环中的一组数据

Question

我相信导致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，则在 WHERE 子句中添加AND sa.StudentId = ?
• 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，则在 WHERE 子句中添加AND q.QuestionId = ?
• 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（下面是它们与示例数据的样子）：

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>

不要忘记我在上面这个问题中提到的 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。

如果您选择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： Luke McFadzen - 下拉值：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的一个或两个中选择 All 选项，则输出仅显示一个学生和一个问题，并且出于某种奇怪的原因，它结合了所有问题的答案并结合了所有学生的答案答案进入单个输出。

现在All 两个下拉菜单中的选项都有一个下拉值0，现在0 不是从数据库中选择的值，但我们在动态 where 子句中声明如果 0 值从特定的下拉菜单中选择，然后从 WHERE 子句中删除相关条件，例如：

• All学生和单个问题（价值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

以上场景存在问题

如果我只是用静态 WHERE 子句 WHERE q.SessionId = ? 离开查询，那么如果我选择 All 学生和 All 问题，它会正确输出详细信息，但我需要该查询适用于从中选择的所有不同可能选项下拉菜单，因此我需要一个动态 WHERE 子句。如何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'] 可能的var_dump：

单个学生和单个问题：

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

单身学生和所有问题：

• 学生：Chris Tucker - string(2) "40"
• 问题：全部 - string(1) "0"

所有学生和一个问题：

• 学生：全部 - string(1) "0"
• 问题：1 - string(1) "72"

所有学生和所有问题：

• 学生：全部 - string(1) "0"
• 问题：全部 - string(1) "0"

如果我选择All 学生和All 问题，以下是var_dump($questions); 示例：

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) 
["answer"]=> 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" } } } }

Answer 1

空() （PHP 4，PHP 5）

empty — 确定变量是否为空 如果 var 则返回 FALSE 存在并且有一个非空的非零值。否则返回 TRUE。

您可能希望为All 选项使用除0 以外的值。