任务：查找每篇文章的最高价格。
SELECT article, MAX(price) AS price FROM shop GROUP BY article ORDER BY article; +---------+-------+ | article | price | +---------+-------+ | 0001 | 3.99 | | 0002 | 10.99 | | 0003 | 1.69 | | 0004 | 19.95 | +---------+-------+