Question

我在Amazon Athena中有一个名为“ levels”的表，该表包括名为“ user”，“ levelstarted”和“ levelcount”的列。该表如下所示： +------+---------------+--------------+ | user | levelstarted | startedcount | +------+---------------+--------------+ | A | 0050 | 2 | | A | 0051 | 1 | | A | 0052 | 3 | | B | 0030 | 1 | | B | 0031 | 2 | | B | 0032 | 5 | | C | 0010 | 6 | | C | 0011 | 3 | | C | 0012 | 3 | +------+---------------+--------------+

对于每个用户，我想要找到一个最高级别的开始，以及玩家开始该级别的次数。我希望得到如下结果：

+------+----------------+----------------+ | user | highestlevel | | startedcount | | +------+----------------+----------------+ | A | 0052 | 3 | | B | 0032 | 5 | | C | 0012 | 3 | +------+----------------+----------------+

找到最高的入门水平就可以了：

SELECT 
 DISTINCT user as payer,
 MAX(levelstarted) as levelstarted
FROM "levels"
GROUP BY user, startedcount

但是当我添加开始计数时，结果中会有重复的用户：

SELECT 
 DISTINCT user as payer,
 MAX(levelstarted) as levelstarted,
 startedcount
FROM "levels"
GROUP BY user, levelcount

Answer 1

在Athena / Presto中，您可以使用max_by函数来查找与列的最大值关联的值：

SELECT
  user,
  MAX(levelstarted) AS highestlevel,
  MAX_BY(startedcount, levelstarted) AS startedcount
FROM (VALUES ('A', '0050', 2),
             ('A', '0051', 1),
             ('A', '0052', 3),
             ('B', '0030', 1),
             ('B', '0031', 2),
             ('B', '0032', 5),
             ('C', '0010', 6),
             ('C', '0011', 3),
             ('C', '0012', 3)
) AS v (user, levelstarted, startedcount)
GROUP BY user
ORDER BY user

计算非重复列的MAX值时出现问题

1 个答案: