使用 cte 和 groupby SQLite 计算中位数

Question

我想使用

SQLite

计算中位数。我感兴趣的变量是将多个表组合在一起的结果。我尝试遵循此解决方案，但输出显示空值。

我的查询如下：

WITH cte AS (
    SELECT m.round,
           f.f * (m.won * o.odds - 1) AS r
    FROM matches m
    INNER JOIN f
    ON f.match_id = m.match_id
        AND f.player_id = m.player_id
    INNER JOIN odds o
    ON o.match_id = m.match_id
        AND o.player_id = m.player_id
)

SELECT round,
       COUNT(*) AS n,
       ROUND(AVG(r), 3) AS avg_r,
       ROUND(AVG(
           CASE counter % 2
               WHEN 0 THEN CASE WHEN rn IN (counter / 2, counter / 2 + 1) THEN r END
               WHEN 1 THEN CASE WHEN rn = counter / 2 + 1 THEN r END
           END
       ) OVER (PARTITION BY round), 3) median_r,
       ROUND(MIN(r), 3) AS min_r,
       ROUND(MAX(r), 3) AS max_r
FROM (
    SELECT *,
    ROW_NUMBER() OVER (PARTITION BY round ORDER BY r) rn,
    COUNT(*) OVER (PARTITION BY round) counter
    FROM cte)
GROUP BY round

我做错了什么？

Answer 1

似乎您的“CASE”和“AVG”功能不正确。像这样的事情就可以了。

    WITH ordered_cte AS (
    SELECT *,
           ROW_NUMBER() OVER (PARTITION BY round ORDER BY r) AS rn,
           COUNT(*) OVER (PARTITION BY round) AS counter
    FROM cte
),
median_cte AS (
    SELECT round,
           CASE
               WHEN counter % 2 = 1 THEN MAX(r) OVER (PARTITION BY round ORDER BY rn ROWS BETWEEN (counter - 1) / 2 AND (counter - 1) / 2)
               ELSE AVG(r) OVER (PARTITION BY round ORDER BY rn ROWS BETWEEN counter / 2 - 1 AND counter / 2)
           END AS median_r
    FROM ordered_cte
)
SELECT round,
       COUNT(*) AS n,
       ROUND(AVG(r), 3) AS avg_r,
       ROUND(MIN(r), 3) AS min_r,
       ROUND(MAX(r), 3) AS max_r,
       ROUND(MAX(median_r), 3) AS median_r
FROM ordered_cte
GROUP BY round;