Question

i have this sql query:

SELECT b.topbid, b.topdate, a.* 
FROM auction_items a 
LEFT JOIN 
   (SELECT itemID, MAX(bid) as topbid, 
   MAX(date) as topdate FROM auction_bids GROUP BY itemID ) b 
ON a.id = b.itemID 
ORDER BY b.topdate DESC, a.date DESC LIMIT 20

It’s not ordering how i’d like it to. I want it to order by merging b.topdate and a.date.

What is wrong?

Answer 1

You cannot have it order by both b.topdate and a.date, because they could both have a value. If you can say that when they both have a value that you should use one over the other (for instance topdate over date), you can do it like this:

SELECT b.topbid, b.topdate, a.* 
FROM auction_items a 
LEFT JOIN 
   (SELECT itemID, MAX(bid) as topbid, 
   MAX(date) as topdate FROM auction_bids GROUP BY itemID ) b 
ON a.id = b.itemID 
ORDER BY COALESCE(b.topdate, a.date) DESC LIMIT 20

Note the order by. If its the other way around, make it COALESCE(a.date, b.topdate)