如何使用GROUP_CONCAT MySQL用PHP循环行

Question

I am triyng to loop the products coming from different categories as shown below:

 $sql = query("SELECT c.name AS 'cat_name', c.image AS 'image', 
                GROUP_CONCAT(DISTINCT p.title ORDER BY p.title DESC SEPARATOR ' ') AS 'product_name' 
                FROM products p 
                INNER JOIN categories c 
                ON p.category_id = c.id 
                GROUP BY p.category_id");
  confirm($sql);

  while($category = mysqli_fetch_array($sql)) {
  $content = <<<DELIMITER


       <li class="col-md-3 col-sm-6">
                <ul>
                  <li class="dropdown-header">{$category['cat_name']}</li>
                  <li><a title="Title" href="#">{$category['product_name']}</a></li>                    

                </ul>
              </li>



 DELIMITER;

 echo $content;
 }

The script above produces following result:

Category name
Product 1 Product 2...

I would like to have the products listed like this:

Category name
Product 1
Product 2
...

What I am doing wrong?

Answer 1

The function GROUP_CONCAT with get you a response of only one line for each category. It will concatenate all your lines with the same category in only one.

You have two possibilities :

1. Using GROUP_CONCAT : each line will contain your Category with all your products concatenated. Then you should split the concatenation of your "Product name's list" to display them correctly.

2. Do not use GROUP_CONCAT : you group your result by the category name. In your loop, you check when the category name change and then change your html accordingly.

---

Edit:

Your variable $category['product_name'] contains the names of your products concatenated by the function GROUP_CONCAT using the delimiter space . If you write

echo $category['product_name']

it will print

Product 1 Product 2...

You can use split() (obsolete) or explode() to separate the products names. And then, you will need to iterate over the array explode() returns to get each Product.

But if your products contains spaces in their names, using GROUP_CONCAT with space as delimiter and split with space as delimiter, you'll get too much results. I advise you tu use another delimiter that can't be use in the product name.

Answer 2

You could use this instead:

SELECT DISTINCT c.name cat_name
              , c.image
              , p.title product_name
           FROM products p   
           JOIN categories c 
             ON p.category_id = c.id;