Multiple values for a column MySQL/CodeIgniter

Question

There are three tables in my application: products , sizes and product_sizes .

The structure is something like this:

products' table:

id INT(11)
name VARCHAR(48)

sizes' table:

id INT(11)
name VARCHAR(48)

product_sizes' table:

id INT(11)
product_id INT(11)
size_id INT(11)

As you can see, there are some products that has three sizes for instance. What I need to show up to the user those three sizes with their names.

What I have in PHP now:

index.php (view)

<?php

[...]

foreach ($products as $product) {
    echo $product->name; // for each item, show its name
}

And I want to iterate with the sizes just like that:

<?php

[...]

foreach ($products as $product) {
    [...]

    echo $product->name;

    foreach($product->sizes as $size) {
        echo $size; // for each item, shows its available sizes (s, M, L, for example)
    }
}

How can I make sizes work together to the products in a consistent way like showed above?

My query, for now is:

SELECT products.id, products.name, sizes.name FROM products
JOIN product_sizes ON product_sizes.product_id = products.id
JOIN sizes ON product_sizes.size_id = sizes.id

---

I marked as CodeIgniter because if there have a way to solve this problem through its ACtiveRecord, no problem because my application runs on the top of CI. You can share your solution normally.

Answer 1

You can use GROUP_CONCAT() in your SQL Query to concat multiple sizes in a one column and later process that cell value.

SELECT products.id, products.name,  GROUP_CONCAT( sizes.name ) available_sizes 
FROM products
     JOIN product_sizes ON product_sizes.product_id = products.id
     JOIN sizes ON product_sizes.size_id = sizes.id
group by products.id

in PHP you can use it as following.

foreach ($products as $product) {
    [...]

    echo $product->name;

    $available_sizes=explode(",",$product->available_sizes);
    foreach($available_sizes as $size) {
        echo $size; // for each item, shows its available sizes (s, M, L, for example)
    }
}

Hope, this helps :)

Answer 2

What you want to do you may achieve it with a bit of SQL, check this, it's an example of getting grouped values (what you want to do) into a single field:

http://sqlfiddle.com/#!2/400994/20

In your case, you'd do something like:

SELECT 
  p.id
, p.name
, CONCAT( "[", GROUP_CONCAT( s.name SEPARATOR ", "), "]" ) sizes
FROM products p
INNER JOIN product_sizes ps
ON ps.product_id = p.id
INNER JOIN sizes s
ON ps.size_id = s.id
GROUP BY p.id

In your PHP, with a json_decode, you'd get the values you wanted.

foreach ($products as $product) {
    [...]

    echo $product->name;
    $product_sizes = json_decode($product->sizes);

    foreach($product_sizes as $size) {
        echo $size; // for each item, shows its available sizes (s, M, L, for example)
    }
}

The advantage of a JSON string, is that when you format it you may get complicated structure data with it.