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：
- 强制 WHERE 条件
q.SessionId = ? - 如果用户从学生下拉菜单中选择单个学生，则添加
AND sa.StudentId = ?到 WHERE 子句 - 如果用户
All从学生下拉菜单中选择学生选项，AND sa.StudentId = ?则从 WHERE 子句中删除或不显示 - 如果用户从问题下拉菜单中选择单个问题，则添加
AND q.QuestionId = ?到 WHERE 子句 - 如果用户
All从问题下拉菜单中选择问题选项，AND q.QuestionId = ?则从 WHERE 子句中删除或不显示
我有三个下拉菜单（下面是示例数据的样子）：
会议：
<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All在学生和问题下拉菜单中的一个或两个中选择一个选项，那么输出只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将所有学生的答案结合到单个输出中。
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，但是我们在动态 where 子句中已经说明，如果0从特定下拉菜单中选择了一个值，则从中删除相关条件WHERE 子句，例如：
All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
如果我只是使用静态 WHERE 子句离开查询，WHERE q.SessionId = ?那么如果我选择All学生和All问题，它会正确输出详细信息，但我需要查询适用于从下拉菜单中选择的所有不同可能选项，因此我需要动态 WHERE条款。我怎样才能让它工作，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 和 的可能$_POST['student']var_dumps $_POST['question']：
单个学生和单个问题：
- 学生：Chris Tucker - string(2) "40"
- 问题：1 - 字符串（2）“72”
单身学生和所有问题：
- 学生：Chris Tucker - string(2) "40"
- 问题：全部 - 字符串（1）“0”
所有学生和一个问题：
- 学生：全部 - 字符串（1）“0”
- 问题：1 - 字符串（1）“72”
所有学生和所有问题：
- 学生：全部 - 字符串（1）“0”
- 问题：全部 - 字符串（1）“0”
以下是var_dump($questions);我选择All学生和All问题的示例：
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" } } } }