MySQL set storing

Question

I have a couple of tables in a web application I'm coding in PHP, and I would like to know if this would be good pratice.

CREATE TABLE `products`(
  `product_id` int NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `variations` varchar(255) default NULL,
  PRIMARY KEY  (`product_id`)
)

CREATE TABLE `variations`(
  `variation_id` int NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `kind` varchar(255) default NULL,
  PRIMARY KEY  (`variation_id`)
)

For example, a product will be:

1,'Cup','1,2,3'

While a variation would be:

1,'Green','Color'
2,'Glass','Texture'
3,'Blue','Color'

such that many products could have the same colors/textures. The issue I find is that I cannot fit this into a single query that would return the data as:

1,'Cup','1,Green,Color-2,Glass,Texture-3,Blue,Color'

And afterwards parse this accordingly to display an image of each variation.

Is a stored function that returns that format the best idea? Or should I normalize even further, and if so, how?

Answer 1

I believe the wise thing to to is add another table:

CREATE TABLE `products_variations`(
  `product_id` int NOT NULL,
  `variation_id` int NOT NULL,
  PRIMARY KEY  (`product_id`, `variation_id`)
);

From there, a simple query joining the three tables will give you the results you need.

Answer 2

SELECT  GROUP_CONCAT(variation_id, ', ', name, ', ', kind SEPARATOR '-')
FROM    products
INNER JOIN
        variations
ON      FIND_IN_SET(variation_id, variations)
GROUP BY
        product_id

As it's a many-to-many relationship, it's better to have a third table:

CREATE TABLE product_variations
(
   product_id INT NOT NULL,
   variation_id INT NOT NULL,
   PRIMARY KEY (product_id, variation_id)
);