此页面是用户选择节目下拉列表的地方，预测摘要将按照下面的屏幕截图显示

• “所选项目”+SelectedProgram+“的学生总数为”+学生总数+“，根据3个学期的数据预测”+城市+“的”+平均总+“学生将在下一学期入学
  。”；

目前，除了+city+之外，所有功能都在工作，有最大学生人数的城市名称应该显示在那里。 我不确定如何用当前的代码添加它。 我尝试了下面的查询，但不起作用。

SELECT DISTINCT student_prg
            , count(student_prg) as countprg
            , count(student_city) as countcity 
         FROM marketing_data
            , current_sem 
        WHERE marketing_data.intake_year = current_sem.intake_year 
        group by student_prg
           , **student_city 
        ORDER 
            by countcity desc 
        LIMIT 1;

选择选项代码

<select id="prg" name="prg"  class="demoInputBox" style="padding: 3px; width: 350px;">
    <option value="">Select Programme</option>

        <?php
        $sql = "SELECT DISTINCT student_prg, count(student_prg) as countprg, count(student_city) as countcity FROM marketing_data, current_sem WHERE marketing_data.intake_year = current_sem.intake_year group by student_prg";

        $do = mysqli_query($conn, $sql);
                          while($row = mysqli_fetch_array($do)){
                            echo '<option value="'.$row['student_prg'].'" data-count="'.$row['countprg'].'" data-count="'.$row['countcity'].'">'.$row['student_prg'].'</option>';
                          }
                      ?>
    </select>

Javascript代码

<script src="//code.jquery.com/jquery-1.12.0.min.js"></script>
<script type="text/javascript">
  var selectedprg = '';
  var selectedcount = '';
  var selectedcity = '';
  var average = '';

  function myFunction() {
    document.getElementById("demo").innerHTML = "The total number of students in the selected program " +selectedprg + " <br>is " +selectedcount + " , it is predicted that " +average+ " students in " +selectedcity+ " will enroll for the upcoming semester <br> based on the data of 3 semesters back.";
  }

  $(document).ready(function(){
    $("#prg").change( function(){
      selectedprg = $('#prg option:selected').text(); 
      selectedcount = $('#prg option:selected').data('count');
      selectedcity = $('#prg option:selected').data('count');
      if(selectedcount > 5){
        average = selectedcount / 3 + 5;
      } else{
        average = selectedcount / 3 - 5;
      }
    });
  });
</script>