Question

我刚使用此代码，并与我合作：

SELECT
* FROM `order` as o
LEFT JOIN `services` as s ON s.`id` = o.`service_id`
LEFT JOIN `users` as u ON u.`id` = o.`users_id`
LEFT JOIN `files` as f ON f.`order_id` = o.`id`

但是当我尝试从第一个表中选择一些字段时，结果没有显示其他表

SELECT
    o.`id` AS `id`,
    o.`service_id`,
    o.`extras`,
    o.`quantity`,
    o.`price`,
    o.`links`,
    o.`keywords`,
    o.`status_id`,
    o.`users_id`,
    o.`date`,
    o.`notes`,
    o.`c_reason`,
    o.`agent_star`
FROM `order` as o
LEFT JOIN `services` as s ON s.`id` = o.`service_id`
LEFT JOIN `users` as u ON u.`id` = o.`users_id`
LEFT JOIN `files` as f ON f.`order_id` = o.`id`

我不知道第二个代码的确切错误是什么，我需要显示表中的所有列：services，users＆amp;档所有列或刚定义的列

Answer 1

当您从联接中选择*时，您正在从所有相关表中选择所有结果。

当您指定订单时，您只获得与订单表相关的结果，如果您要执行SELECT o。*，那么如果您想要查看来自不同表的共享字段，则必须指定它们也在你的select语句中。

基本上你看到了SELECT *和SELECT o。*

之间的区别

Answer 2

这段代码对我有用，谢谢大家：）

SELECT
    o.`id` AS `id`,
    o.`service_id`,
    o.`extras`,
    o.`quantity`,
    o.`price`,
    o.`links`,
    o.`keywords`,
    o.`status_id`,
    o.`users_id`,
    o.`date`,
    o.`notes`,
    o.`c_reason`,
    o.`agent_star`
    s.*
    u.*
    f.*
FROM `order` as o
LEFT JOIN `services` as s ON s.`id` = o.`service_id`
LEFT JOIN `users` as u ON u.`id` = o.`users_id`
LEFT JOIN `files` as f ON f.`order_id` = o.`id`

当我从第一个表中选择一些字段时，SQL无法正常工作

2 个答案: