Aderir à esquerda em MAX(DATE)

SELECT      a.Store_type, a.Date, a.Article, b.Price
FROM        TRANSACTIONS a
LEFT JOIN   PRICES b ON a.Store_type = b.Store_type
AND         a.Article = b.Article
AND         b.Date = (SELECT   MAX (c.Date) 
                      FROM     PRICES c 
                      WHERE    a.Store_type = c.Store_Type
                      AND      a.Article = c.Article
                      AND      c.Date <= a.Date)