SELECT * FROM ScoresTable WHERE Score =
(SELECT MAX(Score) FROM ScoresTable AS st WHERE st.Date = ScoresTable.Date)
Is there a name to describe
There's a much better way to achieve your desired result, using SQL Server's analytic (or windowing) functions.
SELECT DISTINCT Date, MAX(Score) OVER(PARTITION BY Date) FROM ScoresTable
If you need more than just the date and max score combinations, you can use ranking functions, eg:
SELECT *
FROM ScoresTable t
JOIN (
SELECT
ScoreId,
ROW_NUMBER() OVER (PARTITION BY Date ORDER BY Score DESC) AS [Rank]
FROM ScoresTable
) window ON window.ScoreId = p.ScoreId AND window.[Rank] = 1
You may want to use RANK() instead of ROW_NUMBER() if you want multiple records to be returned if they both share the same MAX(Score).