connecting tables through split fields - mysql

Question

I have two tables;
- The Items table - that has basic information about products: name, the basic price of the product, and if the product has any attributes - they will be specified there in the following format: attribute's option ID - attribute's value ID. (an example of an option would be a colour or size, an example of value would be red).
For example:
items table
id | name |attributes |price
1 | a |13-49 | 5.00
2 | b |5-101,13-77| 5.00
3 | c | | 5.00
4 | b |5-102,13-70| 5.00
The second table has every option and value assigned to products (id_option and id_value - meaning the same as in the previous table) as well as information if the attribute value changes the basic price of the product (change) and what the change should be (value).
items_attributes
id |id_item|id_option|id_value |change | value
1 | 1 | 13 | 49 | 1 |10.00
2 | 2 | 5 | 101 | 1 | 5.50
3 | 2 | 13 | 77 | 1 | 0.50
4 | 4 | 5 | 102 | 0 | 0
5 | 4 | 13 | 70 | 1 | 1.00
I want to get a table witch is the same as the first, but with the price calculated according to changes noted in items_attributes table.
id | name |attributes | price
1 | a |13-49 | 15.00
2 | b |5-101,13-77| 11.00
3 | c | | 5.00
4 | b |5-102,13-70| 6.00
How do I split the attributes from the items table and use it to join the two tables?

Answer 1

You can do this with a join using find_in_set():
select i.id, i.name, i.attributes,
i.price + coalesce(sum(ia.value)) as price
from items i left join
items_attributes ia
on find_in_set(concat(ia.id_option, '-', ia.id_attribute), i.attributes) > 0
group by i.id;
Unfortunately, you cannot improve performance of this query using indexes. For better performance, you need a better data structure.