Php Mysql 3表连接

Question

而且我对php有一些困难。我有三张桌子。Table 1 Reference_categories My Table 2 ReferenceTable 3 ref_sel_categories我想进行表之间的内连接，但我无法帮助，你能帮上忙吗？

在我下面写的查询中，只有ids会出现。我想让category_name来。

数据库表

​

​

$query = $db->from('reference')
    ->select('reference.*, GROUP_CONCAT(ref_sel_categories.reference_category_id SEPARATOR \' | \') as categories')
    ->join('ref_sel_categories', 'FIND_IN_SET(%s.reference_id, %s.reference_id)')
    ->orderby('reference_order', 'ASC')
    ->groupBy('reference_id')
    ->all();

?php foreach ($query as $row): ?>
                    <tr>
                        <td width="90"><?= $row['reference_id'] ?></td>
                        <td><?= $row['reference_title'] ?>
                        </td>
                        <td width="200"><?= $row['categories'] ?></td>
                    </tr>
<?php endforeach; ?>

print_r('$row['categories']')
ref_sel_categories is coming The reference_category_id with

Answer 1

我解决了我自己的问题..也许这对其他人有帮助。

$query = $db->from('reference')
    ->select('reference.*, GROUP_CONCAT(reference_categories.category_name SEPARATOR \' | \') as categories')
    ->join('ref_sel_categories', 'reference.reference_id = ref_sel_categories.reference_id ')
    ->join('reference_categories', 'reference_categories.category_id = ref_sel_categories.reference_category_id')
    ->orderby('reference_order', 'ASC')
    ->groupBy('reference_id')
    ->all();