合並兩個表后如何按兩個表中具有相同列名的列排序？

Question

這是兩張表：

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');

我將兩個表的左連接和右連接聯合起來：

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;

但我想從表客戶的 id 訂購結果集：

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 響應是“錯誤代碼：1250。來自 SELECT 之一的表 'c' 不能在全局 ORDER 子句中使用”。 所以我把代碼改成：

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 響應是“錯誤代碼：1052。訂單子句中的列 'id' 不明確”。

我真的很理解這兩個回答，但我也想知道聯合后如何通過客戶的 id 訂購？

Answer 1

是的，您需要通過將當前查詢設置為子查詢來進行全局排序，例如通過單獨別名 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

也許你需要這個：

(
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