SELECT Leaderboard.Name,
(SELECT Actions.Action
FROM Actions
WHERE Actions.Name = Leaderboard.Name
AND Actions.Action LIKE 'Ate%'
ORDER BY Time DESC
LIMIT 1
) AS Latest_Action,
GROUP_CONCAT(Items.Item
ORDER BY Items.Time DESC
SEPARATOR ', '
) AS Items
FROM Leaderboard
LEFT JOIN Items ON Leaderboard.Name = Items.Name
GROUP BY Leaderboard.Name
HAVING Latest_Action IS NOT NULL
ORDER BY Leaderboard.Score DESC
Výsledek ověřen v SQL Fiddle .