合并两个表后如何按两个表中具有相同列名的列排序？

Question

这是两张表：

Create table If Not Exists Customers (Id int, Name varchar(255));
Create table If Not Exists Orders (Id int, CustomerId int);
insert into Customers (Id, Name) values ('1', 'Joe');
insert into Customers (Id, Name) values ('2', 'Henry');
insert into Customers (Id, Name) values ('3', 'Sam');
insert into Customers (Id, Name) values ('4', 'Max');
insert into Orders (Id, CustomerId) values ('1', '3');
insert into Orders (Id, CustomerId) values ('2', '1');
insert into Orders (Id, CustomerId) values ('3', '5');
insert into Orders (Id, CustomerId) values ('4', '6');

我将两个表的左连接和右连接联合起来：

select *
from customers as c
left join orders as o
on c.id = o.customerid

union

select *
from customers as c
right join orders as o
on c.id = o.customerid;

但我想从表客户的 id 订购结果集：

select
*
from
customers as c
left join
orders as o
on
c.id = o.customerid

union

select
*
from
customers as c
right join
orders as o
on
c.id = o.customerid
order by
c.id;

但是 MySQL 响应是“错误代码：1250。来自 SELECT 之一的表 'c' 不能在全局 ORDER 子句中使用”。 所以我把代码改成：

select
*
from
customers as c
left join
orders as o
on
c.id = o.customerid

union

select
*
from
customers as c
right join
orders as o
on
c.id = o.customerid
order by
id;

但是 MySQL 响应是“错误代码：1052。订单子句中的列 'id' 不明确”。

我真的很理解这两个回答，但我也想知道联合后如何通过客户的 id 订购？

Answer 1

是的，您需要通过将当前查询设置为子查询来进行全局排序，例如通过单独别名 id 列：

select *
  from
  (
   select c.id as c_id, c.name, o.id as o_id, o.CustomerId
     from customers as c
     left join orders as o
       on c.id = o.customerid
    union    
   select c.id as c_id, c.name, o.id as o_id, o.CustomerId
     from customers as c
    right join orders as o
       on c.id = o.customerid    
  ) q
 order by q.c_id  

Answer 2

也许你需要这个：

(
select c.id c_id, c.name, o.id o_id
from Customers as c
left join Orders as o on c.id = o.customerid
)
union
(
select o.customerid, c.name, o.id
from Customers as c
right join Orders as o on c.id = o.customerid
)
order by c_id;

小提琴