sql - 如何删除查询的最后一行

Question

我有一张包含我的游戏得分的表格

CREATE TABLE Scores
(
  PlayerName varchar(50),
  LevelId integer,
  Score integer,
  Difficulty integer
);

并且我想始终将分数条目的数量限制为 10 个元素（针对特定级别和难度）

因此，当分数表有 10 个条目（针对特定级别和难度）并且玩家有新的高分时，我想删除最后一个元素（最低分数），并插入新的高分。我怎样才能做到这一点？

Answer 1

怎么样...

DELETE FROM Scores S1
    WHERE Score < (SELECT MIN(Score)
                       FROM (SELECT Score
                                 FROM Scores S2
                                 WHERE S1.Level      = S2.Level      AND
                                       S1.Difficulty = S2.Difficulty
                                 ORDER BY Score DESC
                                 LIMIT 10) AS Derived);

尽管这不适用于每个数据库。If 也不会将表格限制为十行，如果超过一个分数在第十位是水平的。

稍后 - 编辑以纠正 Andomar 指出的错误。

Answer 2

DELETE FROM Scores
WHERE LevelID = ? AND Difficulty = ?
ORDER BY Score ASC
LIMIT 1

应该删除最低分。但即使这是你想要的，也可能不是你需要的。:)

Answer 3

delete from Scores 
where playerName+'|'+cast(levelID as varchar)+'|'+cast(Difficulty as varchar)+'|'+cast(score as varchar) 
in( 
select playerName+'|'+cast(levelID as varchar)+'|'+cast(Difficulty as varchar)+'|'+cast(score as varchar)  from 
(Select rank() over (partition by cast(levelID as varchar)+'|'+cast(Difficulty as varchar) order by score desc) as bRank,* 
from Scores as b) as Ranks
where Ranks.bRank >= 10)

你可以用你的主键替换 playerName+'|'+cast(levelID as varchar)+'|'+cast(Difficulty as varchar)+'|'+cast(score as varchar)

这将为您提供第 10 位及以后的球员：

select Ranks.* from 
(Select rank() over (partition by cast(levelID as varchar)+'|'+cast(Difficulty as varchar) 
order by score desc) as bRank,* 
from Scores as b) as Ranks
where Ranks.bRank >= 10 

结果：

bRank                playerName                                         LevelID     Score       Difficulty
-------------------- -------------------------------------------------- ----------- ----------- -----------
10                   Player 3                                           1           3           10
11                   Player 2                                           1           2           10
12                   Player 1                                           1           1           10