Update rows in table A NOT present in table B

Question

I need to list (and later update) all the items present in the table art who are never referenced in the table orders_items

table art
- artID - artName

Table orders_items
- itemID
- parentID

If i would be looking only by artID=itemID the query is pretty straightforward

select artID, itemID, artName, parentID
FROM art
LEFT JOIN orders_items ON artId=itemID
WHERE stock1=0 and stock3=0 AND itemID is null
GROUP BY artID;

But the problem is that I need to look in itemID AND parentID
Tryed with a subquery but it takes ages and i had to cancel it (art has 30000 records and orders_items near 200000)
In my mind I see an IN() and a GROUP_CONCAT() but I can't get this to work...

Answer 1

I like to keep this post from Jeff bookmarked. I'm not sure how it will perform, but it seems like you could do itemID=artID OR parentID=artID