mysqli子查询未知列

Question

这似乎是一个范围问题 - 子查询中的 select 语句无法识别 table 'candidate':

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

给出错误：“ 'where clause' 中的未知列 'candidate.id'。”如果我输入

而不是 "FROM candidate_pcts p"

FROM candidate_pcts p, candidate c

那么它就看不到 'p.weekly_game_id' ...嗯？

似乎我需要以某种方式为子查询确定 'candidate' table，但我正在尝试的一切只会让我更加误入歧途。而且我尝试了一些乱七八糟的事情：tables 的顺序，在我能想到的任何地方明确标识它们，反引号。我应该注意到嵌套子查询就像一个魅力。又来了：

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'

当然有一个硬编码的 id 值。如果需要，我可以在这里提供数据库结构，但这已经很长了。 'weekly_game' table 只是每个候选人每周的一组分数，我们只需要最近一周的分数，因此 'ORDER BY date DESC LIMIT 1' 子句。

非常感谢您的宝贵时间。

表格：

table candidate:
{id, image, name, party}
table candidate_pcts:
{id, candidate_id, pct, weekly_game_id}
table lineups:
{id, date, user_id}
table players:
{id,candidate_id,lineup_id,order}
table weekly_game:
{id,date}

Answer 1

你基本上是在解决问题的正确轨道上。本质上，嵌套子 select 不知道 candidate.id。如果您分解查询并查看有问题的子select：

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，除了您的 where 子句之外，在该查询中没有对 candidate table 的任何引用，因此这是一个未知列。

因为 subselect 本质上是在引用它的外部 select 之前创建的，subselect 必须是一个独立的 executable 查询.

Answer 2

感谢所有人，尤其是 Mike 的出色解释。我所做的是像这样重组查询：

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

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