如何统计多行并在php中打印行数？

Question

我桌上有很多学生有不同的课程。我想打印一次不同的课程并打印该班级的学生人数。我可以打印课程。但无法打印每个班级的学生人数。我怎样才能做到这一点？例如：

In my database:                       Desired Output:

Class     Name                         Class      Num. of Students
  2       John                           1             2
  2       Snow                           2             3
  3       Jara                           3             1
  1       Peter
  1       Nira
  2       Jerin

这是我的代码：

        $q = "SELECT * FROM ipsc_student group by class";
        $rs = mysql_query($q);
        $numOfRows=mysql_num_rows($rs);

        $rt = "";

        $sl = 0;
            while($row=mysql_fetch_assoc($rs)){
                $sl++;
                $rt.="<tr>";
                $rt.="<td>$sl</td>";
                $rt.="<td>".$row['class']."</td>";
                $rt.="<td>$numOfRows</td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="<td></td>";
                $rt.="</tr>";
            }
            echo $rt;

Answer 1

试试这个

    $q = "SELECT class, count(*) as NUM FROM ipsc_student GROUP BY class";

    $rs = mysql_query($q);
    $numOfRows=mysql_num_rows($rs);

    $rt = "";

    $sl = 0;
        while($row=mysql_fetch_assoc($rs)){
            $sl++;
            $rt.="<tr>";
            $rt.="<td>$sl</td>";
            $rt.="<td>".$row['class']."</td>";
            $rt.="<td>".$row['NUM']."</td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="<td></td>";
            $rt.="</tr>";
        }
        echo $rt;