sql - MySQL join many to many single row

Question

I have 3 tables that I want to combine, see below for details:

product

• productID
• name
• price

prod_cat

• productID
• categoryID

category

• categoryID
• name

joined

product.productID category.categoryID product.name product.price category.name(each one though, since a product can belong to more than one category)

What I want to do is get each product with the categories that relate to them in a single query. How would I got about this?

Answer 1

You need two joins:

SELECT
    product.productID,
    category.categoryID,
    product.name,
    product.price,
    category.name
FROM product
JOIN product_cat ON product.productID = product_cat.productID
JOIN category ON category.categoryID = product_cat.categoryID

If a product could be in no categories and you still want to return it, change JOIN to LEFT JOIN in both places.

An alternative approach:

SELECT
    product.productID,
    product.name,
    product.price,
    GROUP_CONCAT(category.name)
FROM product
JOIN product_cat ON product.productID = product_cat.productID
JOIN category ON category.categoryID = product_cat.categoryID
GROUP BY product.productID

However it might be better just to use two queries instead of putting multiple values into a single cell.