Question

所以我试图将子查询的结果限制为每行一个

    Tables:    
    Companies: id
    Events: id, title, date
    Relations: local_id, foreign_id

select `companies`.*, `e`.`title` 
from `companies` 
left join (
  select `events`.*, `relations`.`local_id` as `pivot_local_id`, `relations`.`foreign_id` as `pivot_foreign_id` 
    from `events` inner join `relations` on `events`.`id` = `relations`.`foreign_id` 
    where `relations`.`local_id` = companies.id 
    order by `date` desc limit 1 
) e on e.pivot_local_id = companies.id

此Q返回＆＃34;＃1054 - 未知列＆＃39; companies.id＆＃39;在＆＃39; where子句＆＃34;。

最后，我想取公司。*以及最新的活动标题＆＃39; （如果有的话）每家公司。

如果可以通过Laravel 5.3的Eloquent ORM完成，我想知道更复杂的事情。

Answer 1

表公司不可见/可用子查询，因此您有错误，主查询中存在的事实不够。

然后你必须加入子查询中的表公司，例如（我不知道子查询是否适合你的范围）

select `companies`.*, `e`.`title` 
from `companies` 
left join (
  select `events`.*, `relations`.`local_id` as `pivot_local_id`, `relations`.`foreign_id` as `pivot_foreign_id` 
    from `events` inner join `relations` on `events`.`id` = `relations`.`foreign_id` 
    inner join companies on `relations`.`local_id` = companies.id 
    order by `date` desc limit 1 
) e on e.pivot_local_id = companies.id

Answer 2

所以，这是你的（不正确的）查询清理：

SELECT c.*, e.title
FROM companies c
LEFT JOIN (
SELECT ev.*, r.local_id AS pivot_local_id, r.foreign_id AS pivot_foreign_id
FROM events ev
INNER JOIN relations r on ev.id = r.foreign_id
WHERE r.local_id = c.id 
ORDER BY `date` DESC LIMIT 1 
) e ON e.pivot_local_id = c.id;

这（希望）应该是您打算实施的内容：

SELECT c.*, ev.title
FROM companies c
LEFT JOIN relations r ON c.id = r.local_id
LEFT JOIN events ev on ev.id = r.foreign_id
WHERE ev.title IS NOT NULL
ORDER BY `date` DESC LIMIT 1;

注意：您可能不需要WHERE ev.title IS NOT NULL，并且应该将date与表别名关联。

祝你好运！

限制/订单结果有3个表

2 个答案: