SQL질문

// list.skin.php $sql = "select group_concat(wr_id) wr_id from $write_table where wr_is_comment = 0 and wr_reply =''	and wr_num >= {$list[0]['wr_num']} order by wr_num";	$result = sql_query($sql); 	$row = sql_fetch_array($result); 	$arr = explode(',', $row['wr_id']); 	foreach ($arr as $k => $v) $no[$v] = $k + 1;		      for ($i=0; $i<count($list); $i++) {      ?>        <tr class="<?php if ($list[$i]['is_notice']) echo "bo_notice"; ?>">            <td class="td_num">            <?php            if ($list[$i]['is_notice']) // 공지사항                echo '<strong>공지</strong>';            else if ($wr_id == $list[$i]['wr_id'])                echo "<span class=\"bo_current\">열람중</span>";            else  echo $no[$list[$i]['wr_id']];             ?>