SQL Inner Join每次都会获取不同的结果

Question

my project stack in this issue bellow ,

i have 2 tables quiziz(filled by teacher) have 10 cols

id,dept,subject,question,ans1,ans2,ans3,ans4,correct_ans,techername

and students have 7 cols

id,username,password,usertype,dept,subject,answers

if the user logged in (successfully) in dborad.php he will see links every link will take him to different quiz in quiz.php page (using get method to get subject and dept for student) , in this quiz.php page he will see his quiz with 4 answers, my problem is the inner join not working , it suppose to fetch quiz for specific subject that he choose from dborad.php with some questions that is different from other students , but its not

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>
                  ";
                }

              }
            }

Answer 1

To fetch diferent question for every user, create a question table and assign an id for each question you want to show your users.

After that, you just need to create a vector with a random function to fetch those questions by id from your database. Change your column question from quizes to question_id which is a foreign key to your recently created table.