Question

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

q.SessionId = ?
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>

不要忘记我在上面提到的WHERE条件是如何工作的。让我们说从会话下拉菜单中选择的会话是POKUB 1, drop down value: 26。

如果您选择单个学生和单个问题，则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选择一个All选项，那么输出只会显示一个学生和一个问题，并且由于一些奇怪的原因，它结合了所有问题的答案并组合了所有学生回答单个输出的答案。

现在两个下拉菜单中的All选项的下拉值都为0，现在0不是从数据库中选择的值，但我们在动态where子句中声明了如果从特定下拉菜单中选择0值，则从WHERE子句中删除相关条件，例如：

All名学生和单个问题（价值72） - WHERE q.SessionId = 26 AND q.QuestionId = 72
单身（价值39）学生和All个问题 - WHERE q.SessionId = 26 AND sa.StudentId = 39
All学生和All个问题 - WHERE q.SessionId = 26

上面的情景有问题

如果我只是使用静态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，但我需要查询才能工作从下拉菜单中选择所有不同的可能选项，因此我需要一个动态WHERE子句。如何让它工作，以便输出正确的细节？

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_dumps：

单身学生和单一问题：

学生：Chris Tucker - 字符串（2）“40”
问题：1 - 字符串（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 - 字符串（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”

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

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   存在且具有非空的非零值。否则返回TRUE。

您可能希望0选项使用All以外的值。

仅显示循环中的一组数据

1 个答案: