假设我有以下表格定义：

CREATE TABLE x (i serial primary key, value integer not null);

我想计算MEDIAN
value（而不是AVG）。中位数是一个将集合划分为两个包含相同数量元素的子集的值。如果元素数为偶数，则中位数是最低细分中的最大值和最大细分中的最低值的平均值。（有关更多详细信息，请参阅Wikipedia。）

这是我设法计算中位数的方法，但我想一定有更好的方法：

SELECT AVG(values_around_median) AS median
  FROM (
    SELECT
       DISTINCT(CASE WHEN FIRST_VALUE(above) OVER w2 THEN MIN(value) OVER w3 ELSE MAX(value) OVER w2 END)
        AS values_around_median
      FROM (
        SELECT LAST_VALUE(value) OVER w AS value,
               SUM(COUNT(*)) OVER w > (SELECT count(*)/2 FROM x) AS above
          FROM x
          GROUP BY value
          WINDOW w AS (ORDER BY value)
          ORDER BY value
        ) AS find_if_values_are_above_or_below_median
      WINDOW w2 AS (PARTITION BY above ORDER BY value DESC),
             w3 AS (PARTITION BY above ORDER BY value ASC)
    ) AS find_values_around_median

有任何想法吗？