테이블 join 질문드립니다. 채택완료

<table>
        <thead>
        <tr>
            <th>순위</th>
            <th>총판장</th>
            <th>구매품목</th>
            <th>판매품목</th>
            <th>총 구매금액</th>
            <th>총 판매금액</th>
        </tr>
        </thead>
        <tbody>
        <?
        $sum_count = "0";
        $sql = "
            select a.mb_id
            , count(*) as cnt, group_concat(a.wr_12 separator '||') wr_12a, group_concat(b.wr_12 separator '||') wr_12b, sum(a.wr_31) as tota, sum(b.wr_31) as totb
            , (select c.mb_name from g5_member c where a.mb_id = c.mb_id) mb_name
            from g5_write_csorder a
            inner join g5_write_cscenter b on a.mb_id = b.mb_id
            where
            a.wr_29 between '{$stx1}' and '{$stx2}' and a.wr_50 like '%{$stx7}%' and NOT a.wr_54 IN ('exchange') and
            b.wr_29 between '{$stx1}' and '{$stx2}' and b.wr_50 like '%{$stx7}%'
            group by a.mb_id ORDER BY tota DESC
        ";
        $result = sql_query($sql, TRUE);
        while ($row = sql_fetch_array($result)) {
        $list_namea = explode('||',$row['wr_12a']);
        $numa = array_count_values($list_namea);

        $list_nameb = explode('||',$row['wr_12b']);
        $numb = array_count_values($list_nameb);

        $sum_count ++
        ?>

        <tr>
            <td class="td_c"><?php echo $sum_count ?>위</td>
            <td class="td_c"><?php echo $row['mb_name'] ?></td>
            <td class="td">
            <?php foreach( $numa as $key => $value ){ ?>
            <?php echo $key; ?>(<?php echo $value?>),
            <?php } ?>
            </td>
            <td class="td">
            <?php foreach( $numb as $key => $value ){ ?>
            <?php echo $key; ?>(<?php echo $value?>),
            <?php } ?>
            </td>
            <td class="td_r"><?php echo number_format(str_replace(',', '', $row['tota']) / 2) ?>원</td>
            <td class="td_r"><?php echo number_format(str_replace(',', '', $row['totb']) / 2) ?>원</td>
        <?php } ?>
        </table>