Question

So, not having come from a database design background, I’ve been tasked with designing a web app where the end user will be entering products, and specs for their products. Normally I think I would just create rows for each of the types of spec that they would be entering. Instead, they have a variety of products that don’t share the same spec types, so my question is, what’s the most efficient and future-proof way to organize this data? I was leaning towards pushing a serialized object into a generic “data” row, but then are you able to do full-text searches on this data? Any other avenues to explore?

Answer 1

split products and specifications into two tables like this:

products
id name

specifications
id name value product_id

get all the specifations of a product when you know the product id:

SELECT  name,
        value
FROM    specifications
WHERE   product_id = ?;

add a specification to a product when you know the product id, the specification’s name and the value of said specification:

INSERT INTO specifications(
    name,
    value,
    product_id
) VALUES(
    ?,
    ?,
    ?
);

so before you can add specifications to a product, this product must exist. also, you can’t reuse specifications for several products. that would require a somewhat more complex solution 🙂 namely…

three tables this time:

products
id name

specifications
id name value

products_specifications
product_id specification_id

get all the specifations of a product when you know the product id:

SELECT  specifications.name,
        specifications.value
FROM    specifications
JOIN    products_specifications
ON      products_specifications.specification_id = specifications.id
WHERE   products_specifications.product_id = ?;

now, adding a specification becomes a little bit more tricky, cause you have to check if that specification already exists. so this will be a little heavier than the first way of doing this, since there are more queries on the db, and there’s more logic in the application.

first, find the id of the specification:

SELECT  id
FROM    specifications
WHERE   name = ?
AND     value = ?;

if no id is returned, this means that said specification doesn’t exist, so it must be created:

INSERT INTO specifications(
    name,
    value
) VALUES(
    ?,
    ?
);

next, either use the id from the select query, or get the last insert id to find the id of the newly created specification. use that id together with the id of the product that’s getting the new specification, and link the two together:

INSERT INTO products_specifications(
    product_id,
    specification_id
) VALUES(
    ?,
    ?
);

however, this means that you have to create one row for every specific specification. e.g. if you have size for shoes, there would be one row for every known shoe size

specifications
id name value
1  size 7
2  size 7½
3  size 8

and so on. i think this should be enough though.