php - 如何在codeigniter中从每个id中选择以逗号分隔的其他表中的多个数据

Question

我有这样的表格

tbl_post

+-----------+--------------+
| post_id   | post_content |
+-----------+--------------+
| 1         |  contentone  |
+-----------+--------------+

tbl_category

+-------------+---------------+
| category_id | category_name |
+-------------+---------------+
|           1 | Politic       |
|           2 | Social        |
|           3 | Economy       |
+-------------+---------------+

tbl_category_post

+------------------+-------------+---------+
| category_post_id | category_id | post_id |
+------------------+-------------+---------+
|                1 |           1 |       1 |
|                2 |           2 |       1 |
|                3 |           3 |       1 |
+------------------+-------------+---------+

然后我想要这样的输出

+--------------+--------------------------+
| post_content |         category         |
+--------------+--------------------------+
|            1 | Politic, Social, Economy |
+--------------+--------------------------+

然后如何使用codeigniter显示这样的数据，我真的很困惑，请任何人帮助我!

Answer 1

编辑:使用 Codeigniter(未测试):

$this->db->select('post_id, GROUP_CONCAT(tc.category_name) AS category_name')
->from('tbl_category_post tcp')
join->('tbl_category tc', 'tc.category_id=tcp.category_id', 'left')
->group_by('tcp.post_id');

我想你需要 PHP 循环方法来循环它。

使用mysql GROUP_CONCAT函数:

SELECT post_id, GROUP_CONCAT(tc.category_name) AS category_name
FROM tbl_category_post tcp
LEFT JOIN tbl_category tc ON tc.category_id=tcp.category_id
GROUP BY tcp.post_id