PostgreSQL

Question

我正在使用 PostgreSQL。
我有一个 table 的竞争对手，其中包含有关电子竞技游戏中竞争对手的信息。 table 包含游戏 ID、参赛者的昵称和所玩角色的名字 he/she。

我想select每个昵称和他们玩得最多的角色。
例如，如果竞争对手 Faker 玩过角色 Ryze 4 次和 Lulu 3 次，我希望 Faker Ryze 4 在输出中。

这是我目前拥有的：

select nick, character, count(*) as played
from competitor
group by nick, character
order by nick;

但是我在输出中得到了 Faker Ryze 4 和 Faker Lulu 3。
我试过 max() 和嵌套，但我无法弄清楚。

Answer 1

你正在使用最大和嵌套走正确的路线，我稍微修改了给定的答案 here:

select t1.nick, t1.character, t1.count
from (
    select nick, character, count(*) as played
    from competitor
    group by nick, character
) t1
inner join
(
  select nick, max(played) max_count
  from 
  (
    select nick, character, count(*) as played
    from competitor
    group by nick, character
  )
  group by nick
) t2
  on t1.nick = t2.nick
  and t1.count = t2.max_count

如果您为基本查询创建了一个视图，这可能更容易阅读：

名为 PlayerCount 的视图：

select nick, character, count(*) as played
from competitor
group by nick, character

SQL 查询现在是：

select t1.nick, t1.character, t1.count
from PlayerCount t1
inner join
(
  select nick, max(played) max_count
  from PlayerCount
  group by nick
) t2
on t1.nick = t2.nick
and t1.count = t2.max_count

Answer 2

这样就可以了。

SELECT nick, character,played
FROM
  (SELECT s1.*,
          row_number() OVER (PARTITION BY nick
                             ORDER BY played DESC) AS row1
   FROM
     (SELECT nick, character, COUNT(*) AS played
      FROM competitor
      GROUP BY nick, character
      ORDER BY nick,
               COUNT(*) DESC) s1)s2
WHERE row1=1;

查询 100% 正确。 SQL Fiddle here。此外，它是唯一可以轻松支持同一昵称的查询（通过将 row_number() 更改为 rank()）并避免不必要的 JOIN.

Answer 3

试试这个：

with counts as (
    select nick, character, count(*) cnt, max(sometimestamp) hora
    from competitor
    group by nick, character
    order by nick, cnt desc, hora
)


select nick, character, max(cnt)
from counts c1 where nick
in (select nick from counts where nick = c1.nick limit 1)
    and character in (select character from counts where nick = c1.nick limit 1)
group by nick, character
order by nick

max(sometimestamp) hora 将成为决胜局，您将不得不适应。或者，如果您不关心关系，只需删除此字段。此查询将为您提供每个昵称的字符，计数较大，如果平局，它将 return 第一个达到最大计数。

PostgreSQL - Select 多个最大计数

PostgreSQL - Select multiple max counts

select

count

max