Mysql SQL错误ORDER BY子句不起作用

ORDERBY子句不使用Union，别名（as）出现错误

信使表

       mid    senderid   receiverid   message   
      ---------------------------------------
        4       100       200          hi
        3       200       100          hello
        2       100       200          hi
        1       100       200          hi

选择语句

  select senderid as new_id from messenger  where  receiverid=200
  union 
  select  receiverid from messenger  where  senderid =200
  order by mid  desc

错误

   #1054 - Unknown column 'mid' in 'order clause'

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我不知道我犯了什么错误，请帮助我提前感谢你的联合结果，你没有中间栏
您只有

新的\u id

你应该加上

select mid, senderid as new_id 
from messenger  where  receiverid=200
union 
select mid, receiverid 
from messenger  where  senderid =200
order by mid  desc

或者避免仅使用单个查询进行联合

select case when senderid = 200 then reciverid else senderid as new_id 
from messenger  
where  receiverid=200 or senderid = 200
order by mid

---

您的联合查询中没有中间字段，所以要么使用中间字段

 select senderid as new_id from messenger  where  receiverid=200
  union 
  select  receiverid as new_id from messenger  where  senderid =200
  order by new_id  desc

或

---

您为什么要使用

联合

select (case when receiverid = 200 then senderid else receiverid end) as new_id
from messenger m
where 200 in (receiverid, senderid)
group by new_id
order by min(mid) desc;

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当UNION时，仅可按顺序使用select列表项。（改为使用UNION ALL。）Mid是一个列，而不是一个字段。@jarlh只是不同的术语，field=column，record=rowWell，不符合ISO/ANSI SQL规范。（可能与Excel文档中的一样？）先生，它可以工作，但我如何使用distinct来忽略多个值的帮助me@CforCODE . . . 我很惊讶你接受了这个答案。你的问题意味着你想要一列而不是两列。更重要的是，这不会删除重复项。@scaisEdge是的，我知道并解决了我的问题，谢谢again@scaisEdge先生，请帮我解决这个问题

select (case when receiverid = 200 then senderid else receiverid end) as new_id
from messenger m
where 200 in (receiverid, senderid)
group by new_id
order by min(mid) desc;