Question

我有一个问题。我想加入一个桌子＆＃34;公司＆＃34;在＆＃34;用户＆＃34;表。问题是，用户既可以是公司的作者/创建者，也可以是会员。

这意味着如果一个字段users.company为空，但字段companies.authorID填充了用户ID或第二种情况，users.company填充了公司ID，而公司.authorID为空。

如何将公司表加入users表呢？

应该像......

LEFT JOIN companies ON companies.id = users.company AND IF users.company = '0' THEN ON companies.authorID = users.id

有没有办法在join子句中实现我想要的东西？

非常感谢！

带有完整子句的当前状态（崩溃查询）

SELECT 
count(users.id),
companies.city AS selectVariable
FROM users 
LEFT JOIN companies ON companies.id = users.company OR (users.company = '0' AND companies.authorID = users.id)
WHERE users.email <> '' AND users.deleted = '0'
GROUP BY companies.city
ORDER BY count(users.id) DESC
LIMIT 20 OFFSET 0

此解决方案正在运行但是def。不像我希望的那样干净......

SELECT 
count(users.id),
    (
    CASE 
        WHEN users.company = '0' THEN c2.city
        WHEN users.company > '0' THEN c.city
        ELSE NULL
    END) AS selectVariable
FROM users 
LEFT JOIN companies c ON c.id = users.company
LEFT JOIN companies c2 ON c2.authorID = users.id
WHERE users.email <> '' AND users.deleted = '0'
GROUP BY selectVariable
ORDER BY count(users.id) DESC
LIMIT 20 OFFSET 0

Answer 1

是的，您可以在or：

中使用join条件

LEFT JOIN companies c ON c.id = u.company 
           OR (u.company = '0' AND c.authorID = u.id)

条件JOIN问题，如果一个字段为空，则选择要加入的其他值

1 个答案: