如何用一个序列化数据联接两列？ [英] How to JOIN two columns with one serialized data?

问题描述

我正在尝试建立一个对产品提供多类别支持的eshop，因此，每当我从< select> 中选择特定类别时，我 serialize（）并将它们保存到数据库中。

I'am trying to build an eshop with multicategory support for products, so whenever I select a specific categories from <select>, I serialize() them and save them into DB.

因此，现在，我要输出JOINed表以及所需的所有数据库数据通过尝试加入两个表： app / models / ecommerce_model中的 CATEGORIES 和 ECOMMERCE_PRODUCTS 。 php ：

So for now, I would like to output the JOINed tables with all db datas I need by trying to join two tables: CATEGORIES and ECOMMERCE_PRODUCTS in my app/models/ecommerce_model.php:

$this->db
    ->select('
            ecommerce_products.id,
            categories.id AS catid,
            categories.title AS categories,
            ecommerce_products.manid,
            ecommerce_products.name
        ')
    ->join('categories', 'ecommerce_products.catid = categories.id', 'left');
    ->join('categories as man', 'ecommerce_products.manid = man.id', 'left');
    $this->db->get('ecommerce_products')->result();

第一个JOIN代表产品类别，第二个JOIN代表产品制造商，它们也存储在<$中c $ c>类别表。

First JOIN stands for product categories, the second JOIN stands for product manufacturers which are also stored in categories table.

因此要澄清一下， ecommerce_products.catid 其中是在第一个JOIN内部被序列化的，我想知道在执行JOIN之前如何将其反序列化吗？

So to clarify, ecommerce_products.catid which is called inside the first JOIN is serialized, and I wonder how to unserialize it before doing a JOIN ?

推荐答案

MySQL不会知道什么是PHP序列化。您可以使用以下格式将类别的ID存储为字符串：

MySQL doesn't know what a PHP serialization is. You could store the IDs of categories as a string in the following format:

2,4,5,10,...

然后，使用 SUBSTRING_INDEX（）和 FIND_IN_SET（） MySQL函数来检查 categories.id ecommerce_products.catid 中的$ c>：

Then, use a combination of SUBSTRING_INDEX() and FIND_IN_SET() MySQL functions to check the existence of categories.id in ecommerce_products.catid:

SUBSTRING_INDEX(
    SUBSTRING_INDEX(ecommerce_products.catid,
        ',',
        FIND_IN_SET(categories.id, ecommerce_products.catid)
), ',', -1)

要为每个产品记录选择类别标题，我们需要通过 GROUP_CONCAT（） 函数，因此最终查询如下：

To select the categories titles for each product record, we need to concatenate the titles by GROUP_CONCAT() function, So the final query would be something like this:

SELECT p.id,
       p.catid
       GROUP_CONCAT(cat.title ORDER BY cat.id SEPARATOR '|') as 'categories',
       p.manid,
       p.name
FROM ecommerce_products AS p
LEFT JOIN categories AS cat
    ON cat.id = SUBSTRING_INDEX(SUBSTRING_INDEX(p.catid, ',', FIND_IN_SET(cat.id, p.catid)), ',', -1)
-- more query...
GROUP BY p.id; -- Group the result to concatenate the categories titles

在这种方法中，您可能需要使用 $ this-> db-> query（）; 方法来手动运行查询。

In this approach, you might need to use $this->db->query(); method to run the query manually.

注意：

，您可以在 ON 语句中使用以下内容：

Note:
As an alternative, you could use the following for ON statement:

LEFT JOIN categories AS cat
    ON p.catid REGEXP CONCAT('[,]{0,1}', cat.id, '[,]{0,1}')

测试用例

这是我的测试用例 SQLFiddle ：

Test-case

Here is my test-case on SQLFiddle:

SELECT p.id,
       p.name,
       GROUP_CONCAT(c.title ORDER BY c.id SEPARATOR '|') as 'categories'
FROM products as p
JOIN categories as c
  ON c.id = SUBSTRING_INDEX(SUBSTRING_INDEX(p.cat_id, ',', FIND_IN_SET(c.id, p.cat_id)) , ',', -1)
GROUP BY p.id;

结果：

Result:

ID    NAME          CATEGORIES
--    ---------     -----------
1     Product 1     Cat 1|Cat 3
2     Product 2     Cat 2|Cat 4
3     Product 3     Cat 1|Cat 4
4     Product 4     Cat 2|Cat 3

这篇关于如何用一个序列化数据联接两列？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！