select語句是否可以包含嵌套的結果集？

Question

考慮下面的表格和樣本數據：

create table Orders (
    ID int not null primary key, 
    Customer nvarchar(100) not null); 

create table OrderItems (
    ID int not null primary key, 
    OrderID int not null foreign key references Orders(ID), 
    Product nvarchar(100) not null); 

insert into Orders values (1, 'John'); 
insert into Orders values (2, 'James'); 
insert into OrderItems values (1, 1, 'Guitar'); 
insert into OrderItems values (2, 1, 'Bass'); 
insert into OrderItems values (3, 2, 'Guitar'); 
insert into OrderItems values (4, 2, 'Drums'); 

我想知道我是否可以查詢父Orders表，也得到了孩子OrderItems表作爲父結果集的結果嵌套。事情是這樣的：

| ORDER.ID | ORDER.CUSTOMER | ORDER.ORDERITEMS     | 
------------------------------------------------------------------ 
|   |    | ORDERITEMS.ID | ORDERITEMS.PRODUCT | 
|   |    |------------------------------------- 
|  1 |   John |    1 |    Guitar | 
|   |    |    2 |    Bass | 
|  2 |   James |    3 |    Guitar | 
|   |    |    4 |    Drums | 

查詢我的想法（這並不在SQL Server的工作）是這樣的：

-- doesn't work, but shows the intent to have nested result sets 
select 
    o.OrderID [Order.ID], o.Customer [Order.Customer], 
    (select 
    oi.ID [OrderItems.ID], oi.Product [OrderItems.Product] 
    from OrderItems oi where o.ID = oi.OrderID 
) [Order.OrderItems] 
from Orders o; 

這只是因爲我想一個概念上的問題想辦法以最小的重複獲得相關數據（例如，與join會發生的情況相反）。

SQL小提琴here。

UPDATE

我從this answer發現，甲骨文與光標表達支持它：

select 
    o.*, 
    cursor(select oi.* from OrderItems oi where o.ID = oi.OrderID) as OrderItems 
from Orders o; 

Answer 1

號這是不是真的有可能。

SQL Server有嵌套關係，不支持NF²

雖然你可以使用FOR XML PATH將其帶回分層方式。

SELECT ID  AS [@ID], 
     Customer AS [@Customer], 
     (SELECT ID  AS [@ID], 
       OrderID AS [@OrderID], 
       Product AS [@Product] 
     FROM OrderItems 
     WHERE OrderItems.OrderID = o.ID 
     FOR XML PATH('OrderItems'), TYPE) 
FROM Orders o 
FOR XML PATH('Order'), ROOT('Orders') 

返回

<Orders> 
     <Order ID="1" Customer="John"> 
     <OrderItems ID="1" OrderID="1" Product="Guitar" /> 
     <OrderItems ID="2" OrderID="1" Product="Bass" /> 
     </Order> 
     <Order ID="2" Customer="James"> 
     <OrderItems ID="3" OrderID="2" Product="Guitar" /> 
     <OrderItems ID="4" OrderID="2" Product="Drums" /> 
     </Order> 
    </Orders> 

此不贅述父Orders