有效的方法來選擇一個固定範圍的高分給予只有一個用戶ID

Question

我有一個表，包括每個球員已經玩過的每場比賽的記錄。我已經得到來自這個問題上回答一個不錯的開端：Ranking with millions of entries，和現在使用的這個查詢檢索每個玩家的最高得分和他們的排名：

SET @rank=0; 

SELECT user_id, score, rank FROM (
    SELECT *, @rank := @rank + 1 as rank 
    FROM high_scores 
    JOIN (
     SELECT user_id as user_id2, MAX(score) AS max_score   
     FROM high_scores 
     GROUP BY user_id2 
     ORDER BY max_score DESC) AS max_score_table     
    ON max_score = high_scores.score AND high_scores.user_id = user_id2) derived_table 
ORDER BY rank; 

再次，這給了我一個很好的有序每個玩家的最高分和列表;不過，我還希望能夠提供特定的user_id，並將結果過濾到此用戶的分數以及X分數的周圍較高和較低分數。

我想我需要執行的「derived_table」一SELECT ... WHERE爲user id和使用返回行的'rank'過濾頂級SELECT聲明，但除了甚至不被接受的查詢（'derived_table不存在'），我這樣做的方式需要我重新查詢derived_table兩次（對於大於和小於測試），這使得查詢效率甚至比它應該低。

如何過濾高分的完整列表並將其排列到單個user_id的條目和X數量的周邊條目？任何關於我試圖提出的代碼（或我現在擁有的代碼）的深入瞭解將不勝感激。

Answer 1

SELECT ranks.rank, ranks.user_id, ranks.maxscore FROM (

    -- find the rank of each user by counting the number of 
    -- users who have a score greater than that user's highest 
    SELECT currentuser.user_id, 
      currentuser.maxscore, 
      IFNULL(COUNT(DISTINCT high_scores.user_id),0) rank 
    FROM  high_scores JOIN (
    -- current user's highest score 
    SELECT user_id, MAX(score) maxscore FROM high_scores GROUP BY user_id 
) currentuser ON high_scores.score > currentuser.maxscore 
    GROUP BY currentuser.user_id 

) ranks JOIN (

    -- find the rank of the user we want similarly 
    SELECT IFNULL(COUNT(DISTINCT user_id),0) rank 
    FROM high_scores JOIN (
    -- our user's highest score 
    SELECT MAX(score) maxscore FROM high_scores WHERE user_id = ? 
) userscore ON high_scores.score > userscore.maxscore 

-- filter for only those who are within given range from our user's rank 
) userrank ON ranks.rank BETWEEN userrank.rank - ? AND userrank.rank + ? 

-- sort the results 
ORDER BY ranks.rank