删除相同的获取数据PHP

<?php
$con = mysqli_connect("localhost","root","","final_osa");
$s_stud = $con->query("SELECT * FROM violations_tbl GROUP BY violation_type");
while($data = $s_stud->fetch_assoc() ){
    $bilang = $con->query("SELECT COUNT(*) FROM violations_tbl WHERE `violation_type` ='".$data['violation_type']."' ");
    $result = $bilang->fetch_assoc();
    if($result['COUNT(*)'] > 1 ){
        echo "<tr>";
            echo "<td>";
                $query=$con->query("SELECT `violation_type` FROM `violations_tbl` WHERE `violation_type`='".$data['violation_type']."'");
                while($row=$query->fetch_assoc() ){
                    echo $row['violation_type'].", ";
                }
                echo "</td>";
                echo "</tr>";
    }
} 
?>

How can i eliminate same fetched data and echo only one? thanks

here is the one that it echoes. it should be that it will echo only one because its the same

What i'm trying to do here is get the mos violated rule in school thanks

If you want all the violations in order of most violated to least violated

$s_stud = $con->query("SELECT violation_type, count(violation_type) as num_violations
                      FROM violations_tbl 
                      GROUP BY violation_type
                      ORDER BY num_violations DESC");

while($row= $s_stud->fetch_assoc() ){
    //echo the violation and the count
    if($row['num_violations'] > 1 ){
        echo "<tr>";
        echo "<td>$row[violation_type]</td>";
        echo "<td>$row[num_violations]</td>";
        echo "</tr>";
    }
}

If you only want the MOST violated you could add a LIMIT 1 to the query and remove the looping.

$s_stud = $con->query("SELECT violation_type, count(violation_type) as num_violations
                      FROM violations_tbl 
                      GROUP BY violation_type
                      ORDER BY num_violations DESC
                      LIMIT 1");

$row= $s_stud->fetch_assoc();
//echo the violation and the count
echo "<tr>";
echo "<td>$row[violation_type]</td>";
echo "<td>$row[num_violations]</td>";
echo "</td></tr>";