Question

我有表用户和项目。

项目有：

project_manager_id -> references users.id
business_manager_id -> references users.id

我必须通过其中一个订购。所以，我的查询是：

select * from projects...
LEFT JOIN profiles project_managers ON project_managers.id = projects.project_manager_id
LEFT JOIN profiles business_managers ON business_managers.id = projects.project_manager_id
order by project_managers.name

OR

order by business_managers.name

但是对于两个顺序，结果都是一样的。我的结果是由第一个profiles.name JOIN（project_managers.name）订购的。

如何通过project_managers.name或business_manager.name正确订购？

Answer 1

这是你想要的吗？

order by coalesce(project_managers.name, business_manager.name)

您使用的是left join，因此假定其中一个值为NULL。

Answer 2

这样的事情会起作用

select * from (
    select projects.id project_id 
    , project_managers.name project_managers_name
    , business_managers.name business_managers_name
    , ...
    from projects
    LEFT JOIN profiles project_managers 
    ON project_managers.id = projects.project_manager_id
    LEFT JOIN profiles business_managers 
    ON business_managers.id = projects.project_manager_id
) projects
order by project_managers_name

按两个别名之一排序（对于同一个表的关系）

2 个答案: