计算不同列的最大值的问题

Question

我在 Amazon Athena 中有一个名为 "levels" 的 table，其中包括名为 "user"、"levelstarted" 和 "levelcount" 的列。 table 看起来像这样： +------+---------------+--------------+ | 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，我想找到开始的最高级别以及玩家开始该级别的次数。我希望得到这样的结果：

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

找到最高的起始级别就可以了：

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，我在结果中得到了重复的用户：

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

计算不同列的最大值的问题

Problem with counting MAX value of distinct column

presto

amazon-athena