Question

这几乎看起来像是范围问题 - 子查询中的select语句无法识别表'候选'：

SELECT 
        candidate.id AS id, 
        candidate.image AS image, 
        candidate.name AS name, 
        candidate.party AS party, 
        player.order AS player_order,
        c_pcts.pct AS pct
FROM  `candidate` 
INNER JOIN players player ON player.candidate_id = candidate.id 
INNER JOIN lineups lineup ON player.lineup_id = lineup.id 
INNER JOIN (
    SELECT 
        pct
    FROM candidate_pcts p
    INNER JOIN weekly_game game ON p.weekly_game_id = (
        SELECT id FROM weekly_game ORDER BY date DESC LIMIT 1
    ) WHERE p.candidate_id = candidate.id 
    ) c_pcts
WHERE lineup.id = '31' 
ORDER BY player.order ASC

在“where子句”中给出错误：“未知列'candidate.id'。”如果不是“FROM candidate_pcts p”，我就把

FROM candidate_pcts p, candidate c

然后它没有看到'p.weekly_game_id'......嗯？

似乎我需要以某种方式识别子查询的“候选”表，但我正在尝试的一切只会让我误入歧途。而且我已经尝试了很多东西：桌子的顺序，明确地识别它们我想到的任何地方，反叛。我应该注意到嵌套的子查询就像一个魅力。这又是：

SELECT pct FROM `candidate_pcts` INNER JOIN weekly_game game ON candidate_pcts.weekly_game_id = ( SELECT id FROM weekly_game ORDER BY date DESC LIMIT 1 ) WHERE candidate_pcts.candidate_id = '5'
当然，
在那里使用硬编码的id值。如果需要，我可以提供数据库结构，但这已经很久了。 'weekly_game'表只是每周每位候选人的一组分数，我们只想要最近一周的分数，因此是“ORDER BY date DESC LIMIT 1”条款。

非常感谢你的时间。

表：

表candidate：
{id，image，name，party}

表candidate_pcts：
{id，candidate_id，pct，weekly_game_id}

表lineups：
{id，date, user_id}

表players：
{id，candidate_id，lineup_id，order}

表weekly_game：
{id，date}

Answer 1

你基本上在问题的正确轨道上。本质上，嵌套的子选择不知道candidate.id。你打破了查询，只看下有问题的子选择：

SELECT 
    pct
FROM candidate_pcts p
INNER JOIN weekly_game game ON p.weekly_game_id = (
    SELECT id FROM weekly_game ORDER BY date DESC LIMIT 1
) WHERE p.candidate_id = candidate.id

您可以看到除了where子句之外，candidate表中的查询没有任何引用，因此这是一个未知列。

由于subselect实质上是在引用它的外部select之前进行的，因此subselect必须是一个独立的可执行查询。

Answer 2

感谢所有人，尤其是迈克的出色解释。我所做的是重新构建了这样的查询：

SELECT 
        candidate.id AS id, 
        candidate.image AS image, 
        candidate.name AS name, 
        candidate.party AS party, 
        player.order AS player_order, 
        pcts.pct AS pct
FROM  `candidate` 
INNER JOIN players player ON player.candidate_id = candidate.id 
INNER JOIN lineups lineup ON player.lineup_id = lineup.id
LEFT JOIN (
    SELECT 
        p.candidate_id AS pct_id, pct AS pct
    FROM candidate_pcts p
    INNER JOIN weekly_game game ON p.weekly_game_id = (
        SELECT id FROM weekly_game ORDER BY date DESC LIMIT 1
    ) 
    ) pcts
        ON pct_id = candidate.id
WHERE lineup.id = '$lineup_id'
ORDER BY player.order ASC

mysqli子查询未知列

2 个答案: