Grabbing the row with the highest value from each group?

问题

I have data that looks like this:

Table
Group: "A" , Color: "Blue", Count: "400"
Group: "A" , Color: "Green", Count: "3"
Group: "A" , Color: "Yellow", Count: "6"
Group: "A" , Color: "Red", Count: "1"
Group: "B" , Color: "Purple", Count: "243"
Group: "B" , Color: "Green", Count: "2"
Group: "B" , Color: "Yellow", Count: "7"

How can I query this data to get for each group the most popular (by count) color. So the result would look like this:

Result
Group: "A", Color: "Blue"
Group: "B", Color: "Purple"

回答1:

SELECT Group, Color
FROM MyTable t
INNER JOIN (SELECT Group, Max(CAST(Count as int)) as Ct
            FROM MyTable
            GROUP BY Group) Sub
   ON sub.group = t.group
   AND sub.ct = t.count

As an aside, don't name a field GROUP, or COUNT. They are keywords and will lead to headaches and heartbreak.

回答2:

This should also work:

SELECT    t.Group,
          t.Color,
          t.Count
FROM     (SELECT   Group,
                   Color,
                   Count,
                   ROW_NUMBER() OVER(PARTITION BY Group ORDER BY CAST(Count AS INT) DESC) AS num
          FROM Table) AS t
WHERE     t.num = 1

来源：https://stackoverflow.com/questions/9180283/grabbing-the-row-with-the-highest-value-from-each-group