在MySQL 5.x中，你可以使用子查询。

SELECT * 
FROM your_table
WHERE (`Group`, Dataset, RunNumber) IN (
    SELECT `Group`, Dataset, MAX(RunNumber) AS MaxRunNumber
    FROM your_table
    GROUP BY `Group`, Dataset
  );

测试 *db<>fiddle here *

备选方案

--
-- LEFT JOIN on bigger
--
SELECT t.* 
FROM your_table t
LEFT JOIN your_table t2
  ON t2.`Group` = t.`Group`
 AND t2.Dataset = t.Dataset
 AND t2.RunNumber > t.RunNumber
WHERE t2.RunNumber IS NULL
ORDER BY t.`Group`, t.Dataset;

--
-- where NOT EXISTS on bigger
--
SELECT * 
FROM your_table t
WHERE NOT EXISTS (
  SELECT 1
  FROM your_table t2
  WHERE t2.`Group` = t.`Group`
    AND t2.Dataset = t.Dataset
    AND t2.RunNumber > t.RunNumber
)
ORDER BY `Group`, Dataset;

--
-- Emulating DENSE_RANK = 1 with variables
-- Works also in 5.x
--
SELECT RunNumber, `Group`, Dataset, Total
FROM
(
  SELECT 
    @rnk:=IF(@ds=Dataset AND @grp=`Group`, IF(@run=RunNumber, @rnk, @rnk+1), 1) AS Rnk
  , @grp := `Group` as `Group`
  , @ds := Dataset as Dataset
  , @run := RunNumber as RunNumber
  , Total
  FROM your_table t
  CROSS JOIN (SELECT @grp:=null, @ds:=null, @run:=null, @rnk := 0) var
  ORDER BY `Group`, Dataset, RunNumber DESC
) q
WHERE Rnk = 1
ORDER BY `Group`, Dataset;

--
-- DENSE_RANK = 1
-- MySql 8 and beyond. 
--
SELECT *
FROM
(
  SELECT *
  , DENSE_RANK() OVER (PARTITION BY `Group`, Dataset ORDER BY RunNumber DESC) AS rnk
  FROM your_table
) q
WHERE rnk = 1
ORDER BY `Group`, Dataset;