1

sqlfiddle：http ://sqlfiddle.com/#!2/9a8b3/1

从小提琴中获取结构、数据和查询，导入我的 MariaDB 5.5.31，我得到不同的结果：

sqlfiddle

PID  NAME       LEAGUEPOINTS        TOTALLEAGUEPOINTS
2   Peter   16,13,9,4,2            44
1   Daniel  3425,543,234,43,29,22,21,21,19,17,13,12,12,12,11,9,9,9,8,7      4476

玛丽亚数据库

pid  name    leaguepoints       totalleaguepoints   
2   Peter   16,13,9,4,2             44
1   Daniel  3425,543,234,43,29,22,21,21,19,17,13,12,12,12,11,9,9,9,8,7,7,6,5,5,4,4,4,3,3,2,1    4520

询问：

SELECT                
    p.pid,
    p.name,   
    GROUP_CONCAT( gC.leaguepoints ORDER BY leaguepoints DESC ) AS leaguepoints, 
    SUM(gC.leaguepoints) AS totalleaguepoints
FROM test_golf_player p
LEFT JOIN 
(
    SELECT pid, leaguepoints, @Sequence:=IF(@PrevPid = pid, @Sequence + 1, 0) AS aSequence, @PrevPid := pid
    FROM
    (
        SELECT pid, leaguepoints
        FROM test_golf_card 
        ORDER BY pid, leaguepoints DESC
    ) Sub1
    CROSS JOIN (SELECT @PrevPid := 0, @Sequence := 0) Sub2
) gC
ON p.pid = gC.pid AND aSequence < 20
GROUP BY p.pid
ORDER BY p.name DESC

知道为什么吗？

4

1 回答 1

1

恐怕我手头没有 MariaDB，但是您可以尝试以下操作以查看用户变量的输出方式：-

SELECT  *
FROM test_golf_player p
LEFT JOIN 
(
    SELECT pid, leaguepoints, @Sequence:=IF(@PrevPid = pid, @Sequence + 1, 0) AS aSequence, @PrevPid := pid
    FROM
    (
        SELECT pid, leaguepoints
        FROM test_golf_card 
        ORDER BY pid, leaguepoints DESC
    ) Sub1
    CROSS JOIN (SELECT @PrevPid := 0, @Sequence := 0) Sub2
) gC
ON p.pid = gC.pid 
ORDER BY p.name DESC

编辑 - 对您的结果进行一些调查，似乎 MariaDB 忽略了子查询中的 ORDER BY。因此，序列号是随机顺序的，并且在 pid 更改时也会重置（由于顺序不固定，它会随机执行）。有点谷歌，这似乎是 MariaDB 的一个故意的功能。SQL 标准将表定义为一组无序的行，并且子选择被视为表，因此忽略 order by - https://kb.askmonty.org/en/why-is-order-by-in -a-from-subquery-ignored/。

这有点不利。不确定是否有解决方法，因为我目前想不出一个。对于要处理的原始问题，我认为有必要使用可能效率不高的相关子选择。

于 2013-07-09T11:38:37.187 回答