mysql - 如何获取每组中的最大值和最小值以及它们的时间？

Question

假设我有一个包含 Id、NumericValue 和 UTCTimestamp 列的表 MyTable。我正在尝试按时间戳的小时对表 MyTable 的结果进行分组，并返回每个组的最大数值及其相关时间戳以及每个组的最小数值及其相关时间戳值。

现在，我可以通过以下查询来解决问题的第一部分:

SELECT 
    HOUR(t.UTCTimestamp) AS `Hour`, 
    t.NumericValue AS MaximumValue,
    t.UTCTimestamp AS MaximumValueTime
FROM MyTable t
INNER JOIN (
    SELECT HOUR(t2.UTCTimestamp) AS `Hour`, MAX(t2.NumericValue) AS NumericValue
    FROM MyTable t2
    GROUP BY HOUR(t2.UTCTimestamp)
) maxNumericValue ON HOUR(t.UTCTimestamp) = maxNumericValue.`Hour` AND t.NumericValue = maxNumericValue.NumericValue
GROUP BY HOUR(t.UTCTimestamp);

灵感来自 this answer .

Here's an MVCE .

如何显示每个组的最小值以及与之关联的时间戳？

Answer 1

从 MySQL 8.0 开始，您可以使用 ROW_NUMBER:

WITH cte AS (
  SELECT *,ROW_NUMBER() OVER(PARTITION BY HOUR(UTCTimestamp) 
                              ORDER BY UTCTimestamp ASC)  AS rn
          ,ROW_NUMBER() OVER(PARTITION BY HOUR(UTCTimestamp) 
                              ORDER BY UTCTimestamp DESC) AS rn2
  FROM MyTable
)
SELECT HOUR(c1.UTCTimestamp),
     c1.ID, c1.NumericValue, c1.UTCTimestamp,  -- min row
     c2.ID, c2.NumericValue, c2.UTCTimestamp   -- max row
FROM cte c1
JOIN cte c2
  ON HOUR(c1.UTCTimestamp) = HOUR(c2.UTCTimestamp)
  AND c1.rn=1
  AND c2.rn2=1
ORDER BY HOUR(c1.UTCTimestamp) ASC;

DBFiddle Demo