Question

I have not worked with SQL for quite a long time, and I need some help for a basic query. I have the three following tables:

• users (id, name)
• products (id, name)
• owners (userid, productid, date)

One product can be sold by user A to user B and then back to A.

Now, I want the list of all products currently owned by every single user with the date of transaction.

Currently, my query is this one, but I’m stuck with old data (first association of one product to one user, and not the newest one):

SELECT users.name, products.name, date
FROM products
     JOIN owners ON products.id = owners.id
     JOIN users ON owners.id = user.id
GROUP BY product.id

Do you have some hints?

Thanks

Answer 1

you need to add a subquery which gets that latest date for each productid

SELECT  users.name, 
        products.name, 
        date
FROM    products
        JOIN owners 
            ON products.id = owners.id
        JOIN users 
            ON owners.id = user.id
        JOIN
        (
            SELECT productID, MAX(Date) maxDATE
            FROM owners
            GROUP BY productID
        ) nw ON owners.productID = nw.productID AND
                owners.date = nw.maxDAte
GROUP BY product.id