我有一个比赛表,大致如下:
player_id | match_id | result | opponent_rank
----------------------------------------------
82 | 2847 | w | 42
82 | 3733 | w | 185
82 | 4348 | l | 10
82 | 5237 | w | 732
82 | 5363 | w | 83
82 | 7274 | w | 6
51 | 2347 | w | 39
51 | 3746 | w | 394
51 | 5037 | l | 90
... | ... | ... | ...
为了获得所有连胜(不仅仅是任何玩家的最高连胜),我使用以下查询:
SELECT player.tag, s.streak, match.date, s.player_id, s.match_id FROM (
SELECT streaks.streak, streaks.player_id, streaks.match_id FROM (
SELECT w1.player_id, max(w1.match_id) AS match_id, count(*) AS streak FROM (
SELECT w2.player_id, w2.match_id, w2.win, w2.date, sum(w2.grp) OVER w AS grp FROM (
SELECT m.player_id, m.match_id, m.win, m.date, (m.win = false AND LAG(m.win, 1, true) OVER w = true)::integer AS grp FROM matches_m AS m
WHERE matches_m.opponent_position<'100'
WINDOW w AS (PARTITION BY m.player_id ORDER BY m.date, m.match_id)
) AS w2
WINDOW w AS (PARTITION BY w2.player_id ORDER BY w2.date, w2.match_id)
) AS w1
WHERE w1.win = true
GROUP BY w1.player_id, w1.grp
ORDER BY w1.player_id DESC, count(*) DESC
) AS streaks
ORDER BY streaks.streak DESC
LIMIT 100
) AS s
LEFT JOIN player ON player.id = s.player_id
LEFT JOIN match ON match.id = s.match_id
结果如下所示(请注意,这不是固定的表/ View ,因为上面的查询可以通过某些参数进行扩展,例如国籍、日期范围、玩家排名等):
player_id | match_id | streak
-------------------------------
82 | 3733 | 2
82 | 7274 | 3
51 | 3746 | 2
... | ... | ...
我现在想要添加的是一堆汇总数据,以提供有关连胜的详细信息。首先,我想知道每次连胜期间对手的平均排名。其他数据包括连续的持续时间、第一个和最后一个日期、结束连续的对手姓名或连续的对手名称,等等。我尝试过各种方法 - CTE、一些精心设计的联接、联合,或者将它们作为滞后函数添加到现有代码中。但我完全不知道如何解决这个问题。
从代码中可以明显看出,我的 SQL 技能非常基础,所以请原谅任何错误或低效的语句。对于完整的上下文,我在 Debian 上使用 Postgres 9.4,matches_m 表是一个具有 550k 行的物化 View (查询现在需要 2.5 秒)。数据来自http://aligulac.com/about/db/ ,我只是镜像它来创建上述 View 。
最佳答案
我认为这符合你的要求。
关键思想是为每个连胜分配一个“连胜组”,这样您就可以将它们聚合起来。您可以通过观察来做到这一点:
- 一场连胜的比赛显然是一场“胜利”。
- 可以通过计算之前的失败次数来识别连胜 - 这对于连胜来说是恒定的。
Postgres 在 9.4 中引入了 filter
子句,这使得语法变得更简单:
select player_id, count(*) as streak_length,
avg(opponent_rank) as avg_opponent_rank
from (select m.*,
count(*) filter (where result = 'l') over (partition by player_id order by date) as streak_grp
from matches_m m
) m
where result = 'w'
group by player_id, streak_grp;
关于sql - 如何从相邻表中动态数量的相关行获取聚合数据,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/52024244/