how do I update the value of each row without primary key? - php

Question

I want to update the value in a certain row. But it seems impossible since this table (from database) doesn't have the primary key. It only have two foreign key in its column. What should I do ? please, any help ?
here is my code :
<table align= "center" border="1" cellspacing="0" cellpadding="2">
<?php
$strgettable="select tblUsrGrp.UsrGrpNama, tblmenu.MenuNama, tblmenuakses.MenuAkses
FROM tblUsrGrp
inner join tblMenuAkses
on tblUsrGrp.UsrGrpID = tblMenuAkses.usrgrpid
inner join tblMenu
on tblMenu.menuid = tblMenuAkses.menuid";
$varRecCount=0;
$rs=odbc_exec($dbconnVOT, $strgettable);
if($rs)
{
echo '<tr><td style=width:10%;>';
echo '<center><b> No. </b></center>';
echo '</td>';
echo '<td style=width:30%;>';
echo '<center><b> User Group </b></center>';
echo '</td>';
echo '<td style=width:20%;>';
echo '<center><b> Menu Name </b></center>';
echo '</td>';
echo '<td style=width:20%;>';
echo '<center><b> Menu Akses </b></center>';
echo '</td>';
echo '<td style=width:20%;>';
echo '<center><b> Update </b></center>';
echo '</td></tr>';
while (odbc_fetch_row($rs))
{
$varRecCount++;
echo '<tr><td>';
echo '<center> '.$varRecCount.'</center>';
echo '</td>';
echo '<td>';
echo '<center> '.odbc_result($rs,"UsrGrpNama").'</center>';
echo '</td>';
echo '<td>';
echo '<center> '.odbc_result($rs,"MenuNama").'</center>';
echo '</td>';
echo '<td>';
echo '<center> '.odbc_result($rs,"MenuAkses").'</center>';
echo '</td>';
echo '<td>';
echo '</td>';
echo '</td></tr>';
}
}
?>
</table>
<div style="text-align:center;">
<input type="button" name="btnUpdate" id="btnUpdate" onClick="javascript:sendData('updatedata');" value = "Update">
</div>
any help would be much appreciated . TQ