Using GROUP_CONCAT on subquery in MySQL

Question

I have a MySQL query in which I want to include a list of ID\'s from another table. On the website, people are able to add certain items, and people can then add those items to

Answer 1

You can't access variables in the outer scope in such queries (can't use items.id there). You should rather try something like

SELECT
    items.name,
    items.color,
    CONCAT(favourites.userid) as idlist
FROM
    items
INNER JOIN favourites ON items.id = favourites.itemid
WHERE
    items.id = $someid
GROUP BY
    items.name,
    items.color;

Expand the list of fields as needed (name, color...).