Untitled

$sql = "
SELECT DISTINCT
       CONCAT(CAST(t1.MR_ID AS INT),' - ', COALESCE(t2.MR_Name, '')) AS MR_ID,
       t1.MR_ID AS sort_column
FROM Stage_Rebate_Index t1
      LEFT JOIN Stage_Rebate_Master t2
         ON t2.MR_ID = t1.MR_ID
ORDER BY sort_column";

$sql_one = "
SELECT
       CONCAT(CAST(t1.MR_ID AS INT),' - ', COALESCE(t2.MR_Name, '')) AS MR_ID,
       t1.MR_ID AS sort_column,
       CAST(Supp_ID as INT) AS Supp_ID
FROM Stage_Rebate_Index t1
      LEFT JOIN Stage_Rebate_Master t2
         ON t2.MR_ID = t1.MR_ID
WHERE
  CONCAT(CAST(t1.MR_ID AS INT),' - ', t2.MR_Name) = LTRIM(RTRIM('$mr_id'))
ORDER BY sort_column";

function updatetable(myForm) {

    function show() { document.getElementById('index-table').style.display = 'block'; }


    var selIndex = myForm.selectedIndex;
    console.log();
    var selName = $( "#mr_id option:selected" ).text();

// Ajax sends POST method to Stage_Rebate_Index table and pulls information based on drop down selection
$.ajax ({
    url: "test-table.php",
    method: "POST", //can be post or get, up to you
    data: {
        mr_id : selName
    },
    beforeSend: function () {
        //Might want to delete table and put a loading screen, otherwise ignore this
    },
    success: function(data){
        $("#table_div").html(data); // table_div is the div you're going to put the table into, and 'data' is the table itself.
        console.log(data);
        console.log(selName)
    }
 });

}

<?php
$host="xxxxxxxx";
$dbName="xxxx";
$dbUser="xxxxxxxxxx";
$dbPass="xxxxxxxx";

$mr_id = $_POST['mr_id'];

$dbh = new PDO( "sqlsrv:server=".$host."; Database=".$dbName, $dbUser, $dbPass);
$dbh->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
//$sql = "SELECT DISTINCT CAST(MR_ID AS INT) AS MR_ID FROM Stage_Rebate_Index WHERE MR_ID = '$mr_id'";
//$sql_one = "SELECT CAST(Supp_ID AS INT) AS Supp_ID, CAST(MR_ID AS INT) AS MR_ID FROM Stage_Rebate_Index WHERE MR_ID = '$mr_id'";

$sql_one = "
SELECT
       CONCAT(CAST(t1.MR_ID AS INT),' - ', COALESCE(t2.MR_Name, '')) AS MR_ID,
       t1.MR_ID AS sort_column,
       CAST(Supp_ID as INT) AS Supp_ID
FROM Stage_Rebate_Index t1
      LEFT JOIN Stage_Rebate_Master t2
         ON t2.MR_ID = t1.MR_ID
WHERE
  CONCAT(CAST(t1.MR_ID AS INT),' - ', t2.MR_Name) = LTRIM(RTRIM('$mr_id'))
ORDER BY sort_column";

//$users = $dbh->query($sql);
$users_one = $dbh->query($sql_one);
?>

<html>
    <body>

        <!-- Table -->
<p>
    <div id="table_div">
        <table border="1" id="index_table" class="ui-widget ui-widget-content">
            <thead>
                <tr class="ui-widget-header">
                <td>MR ID</td>
                <td>Supplier ID</td>
                </tr>
            </thead>
            <?php foreach($users_one->fetchAll() as $supp) { ?>
            <tr>
                <td class="mr_id"><?php echo $supp['MR_ID'];?></td>
                <td class="supp_id"><?php echo $supp['Supp_ID'];?></td>
            </tr>
            <?php } ?>
        </table>
    </div>

    </body>
    </html>