mysql - 如何获取每组中的最大值和最小值以及它们的时间？

Question

假设我有一个表 MyTable，其中包含 Id、NumericValue 和 UTCTimestamp 列。我试图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 NumericValue 及其关联的时间戳，以及每个组的最小 NumericValue 及其关联的时间戳值。

现在，我可以通过以下查询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 .

我怎样才能显示每个组的最小值以及与其关联的时间戳？

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;

<强> DBFiddle Demo