Question

我有以下表格：

1） tbl_entries ：

+----------+-------------+-------------------+
| entry_id | entry_title | entry_category_id |
+----------+-------------+-------------------+
| 10       | Entry 1     | 3                 |
| 20       | Entry 2     | 2                 |
| 30       | Entry 3     | 2                 |
| 40       | Entry 4     | 5                 |
+----------+-------------+-------------------+

2） tbl_categories

+-------------+---------------+
| category_id | category_name |
+-------------+---------------+
| 1           | Animal        |
| 2           | People        |
| 3           | Gadgets       |
| 4           | Entertainment |
| 5           | Business      |
+-------------+---------------+

2） tbl_categories_secondary

+-------------+---------------+
| cs_entry_id | cs_category_id|
+-------------+---------------+
| 10          | 5             |
| 20          | 1             |
| 20          | 3             |
| 20          | 5             |
| 40          | 1             |
| 40          | 4             |
+-------------+---------------+

我想查询所有条目及其主要和次要类别（ 按字母顺序排列并以逗号分隔 ），这样会导致：

+-------------+---------------------------------+
| title       | categories                      |
+-------------+---------------------------------+
| Entry 1     | Business,Gadgets                |
| Entry 2     | Animal,Business,Gadgets,People  |
| Entry 3     | People                          |
| Entry 4     | Animal,Business,Entertainment   |
+-------------+---------------------------------+

这是我几乎一天没有运气的尝试：

SELECT tbl_entries.entry_title AS title, addCats.more_categories AS categories
FROM tbl_entries,
(
    SELECT cs_entry_id, GROUP_CONCAT(category_name SEPARATOR ',') AS more_categories
    FROM tbl_categories
    INNER JOIN tbl_categories_secondary
        ON tbl_categories.category_id = tbl_categories_secondary.cs_category_id
    GROUP BY cs_entry_id
) addCats
INNER JOIN categories
    ON tbl_entries.entry_category_id = tbl_categories.category_id

我现在的问题是如何获取条目的主要和所有次要类别，并将它们混合/放入一列，如上所述。

任何帮助将不胜感激：）

Answer 1

尝试类似下面的内容。为tbl_categories创建别名为tc1并加入

选择tbl_entries.entry_title，concat（group_concat（tbl_categories.category_name），group_concat（tc1.category_name）） tbl_entries.entry_category_id = tbl_categories.category_id上的内连接tbl_categories tbl_categories_secondary.cs_entry_id = tbl_entries.entry_id上的内连接tbl_categories_secondary 内联接tbl_categories为tc1 on tc1.category_id = tbl_categories_secondary.cs_category_id group by tbl_entries.entry_title

MySQL嵌套和Concat两列？

1 个答案: