mysql在單個表格中選擇每個類別的最佳

Question

假設我有一個名爲Gamers的表格。 遊戲玩家包含列GamerID,GameID,Score。

我有興趣選擇每場比賽得分最高的球員。

例如，

|Gamers 
|------------------------- 
|GamerID | GameID | Score 
|1  | 1  | 10 
|2  | 1  | 10 
|3  | 1  | 10 
|4  | 1  | 90 
|5  | 2  | 40 
|6  | 2  | 10 
|7  | 3  | 10 
|8  | 3  | 30 

查詢，我希望得到的行，GamerID 4，5和8是什麼，會做這樣的查詢後？

Answer 1

試試這個：

SELECT gamers.* 
FROM gamers 
INNER JOIN 
(SELECT 
    max(score) as maxscore, 
    gameid from gamers 
    GROUP BY gameid) AS b 
ON (b.gameid = gamers.gameid AND b.maxscore=gamers.score) ; 
ORDER BY score DESC, gameid; 

這將輸出：

+---------+--------+-------+ 
| gamerid | gameid | score | 
+---------+--------+-------+ 
|  4 |  1 | 90 | 
|  5 |  2 | 40 | 
|  8 |  3 | 30 | 
+---------+--------+-------+ 
3 rows in set (0.00 sec) 

你可以做的另一種選擇是創建臨時表或視圖（如果你不喜歡子查詢）。

create temporary table games_score (
SELECT max(score) as maxscore, gameid FROM gamers GROUP BY gameid 
); 

然後：

SELECT gamers.* 
FROM gamers 
INNER JOIN games_score AS b ON (b.gameid = gamers.gameid AND b.maxscore=gamers.score) 
ORDER BY score DESC, gameid; 

或視圖：

create or replace view games_score AS 
SELECT max(score) as maxscore, gameid FROM gamers GROUP BY gameid; 

然後：

SELECT gamers.* 
FROM gamers 
INNER JOIN games_score AS b ON (b.gameid = gamers.gameid AND b.maxscore=gamers.score) 
ORDER BY score DESC, gameid; 

Answer 2

你可以這樣使用一個子選擇，像下面完成：

SELECT GameID, GamerID, Score 
FROM Gamers 
WHERE Score = (
    SELECT 
    MAX(scores.Score) 
    FROM Gamers AS scores 
    WHERE scores.GameID = Gamers.GameID 
) 
GROUP BY GameID 

測試上：

CREATE TABLE Gamers (
    GamerID int(11) NOT NULL, 
    GameID int(11) NOT NULL, 
    Score int(11) NOT NULL 
) ENGINE=MyISAM DEFAULT CHARSET=latin1; 

INSERT INTO Gamers (GamerID, GameID, Score) VALUES 
(1, 1, 10), 
(2, 1, 10), 
(3, 1, 10), 
(4, 1, 90), 
(5, 2, 40), 
(6, 2, 10), 
(7, 3, 10), 
(8, 3, 10); 

當然這不會是在兩個玩家達到特定的遊戲分數相同的情況下的理想選擇。

Answer 3

試試這個：

SELECT a.GameID, a.GamerID, a.Score 
FROM Gamers a INNER JOIN 
    (
     SELECT s.GameID, MAX(s.Score) AS Maxx 
     FROM Gamers s 
     GROUP BY s.GameID 
    ) b ON (a.GameID = b.GameID) AND (a.Score = b.Maxx) 
ORDER BY GameID; 

Answer 4

試試這個：

select g1.* from gamers g1 
left join gamers g2 
on g1.gameId = g2.gameId and g1.score < g2.score 
where g2.score is null 

結果給提供的數據顯示：

+---------+--------+-------+ 
| GAMERID | GAMEID | SCORE | 
+---------+--------+-------+ 
|  4 |  1 | 90 | 
|  5 |  2 | 40 | 
|  8 |  3 | 30 | 
+---------+--------+-------+ 

Answer 5

看這裏http://dev.mysql.com/doc/refman/5.0/en/example-maximum-column-group-row.html