[英]SQL Inner Join fetch different results every time
我在這個問題中的項目堆棧如下
我有2張桌子測驗 (由老師填寫)有10列
id,部,主題,問題,ans1,ans2,ans3,ans4,correct_ans,技術名稱
學生有7個山口
ID,用戶名,密碼,用戶類型,部門,主題,答案
如果用戶(成功)登錄dborad.php,他將看到鏈接,每個鏈接將帶他進入quiz.php頁面中的其他測驗( 使用get方法獲取學生的主題和部門 ),在此quiz.php頁面中,他將看到他的測驗有4個答案,我的問題是內部聯接不起作用,它假設要從dborad.php中獲取他選擇的特定主題的測驗,但有一些與其他學生不同的問題,但它不是
dboard.php
if (isset($_SESSION['username'])) {
if ($_SESSION['usertype'] === "isstudent") {
$SQLgetParea = "SELECT * From students WHERE username = '$_SESSION[username]' ";
$SQLgetPareaResult = mysqli_query($conn,$SQLgetParea);
$SQLgetPareaRow = mysqli_fetch_array($SQLgetPareaResult,MYSQLI_NUM);
$getDept = $SQLgetPareaRow[4];
$sql2 = "SELECT students.*, quiziz.*
FROM students
INNER JOIN quiziz
ON students.dept=quiziz.dept
AND students.subject = quiziz.subject
WHERE students.dept = '".$getDept."'
";
$result2 = mysqli_query($conn,$sql2);
while ($row2 = mysqli_fetch_array($result2,MYSQLI_NUM)) {
echo "
<a href='quiz.php?subject=".$row2[5]."?dept=".$row2[4]."'>Enter Exam for ".$row2[5]."</a>
<br><br>";
}
}
}
quiz.php
if(isset($_SESSION['username'])){
if ($_SESSION['usertype'] === "isstudent") {
$conn->query("SET NAMES utf8");
$conn->query("SET CHARACTER SET utf8");
$SQLgetParea = "SELECT * From students ";
$SQLgetPareaResult = mysqli_query($conn,$SQLgetParea);
$SQLgetPareaRow = mysqli_fetch_array($SQLgetPareaResult,MYSQLI_ASSOC);
$getSub = $SQLgetPareaRow['subject'];
$sql2 = "SELECT quiziz.*, students.*
FROM quiziz
INNER JOIN students
ON quiziz.dept=students.dept
AND quiziz.subject = '".$getSub."' ";
$result2 = mysqli_query($conn,$sql2);
while ($row2 = mysqli_fetch_array($result2,MYSQLI_ASSOC)) {
echo "
<li>".$row2['question']."</li>
<li><div class='ruler'></div></li>
<li>".$row2['ans1']."</li>
<li>".$row2['ans2']."</li>
<li>".$row2['ans3']."</li>
<li>".$row2['ans4']."</li>
";
}
}
}
要為每個用戶獲取不同的問題,請創建一個問題表,並為要顯示給用戶的每個問題分配一個ID。
之后,您只需要創建一個帶有隨機函數的向量即可通過id從數據庫中獲取這些問題。 將列問題從測驗更改為question_id,這是您最近創建的表的外鍵。
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