JOIN FOR SYSTEM TIME 以列作为有效系统时间

Question

想象一下，我有一个模式，其中包括Products，Orders，和OrderLineItems，与Products作为一个系统版本态表。

架构：

CREATE TABLE dbo.Products
(
    ProductID INT NOT NULL IDENTITY PRIMARY KEY,
    Name nvarchar(255) not null,
    SysStart DATETIME2 (7) GENERATED ALWAYS AS ROW START NOT NULL,
    SysEnd DATETIME2 (7) GENERATED ALWAYS AS ROW END NOT NULL,
    PERIOD FOR SYSTEM_TIME ([SysStart], [SysEnd])
)
WITH (SYSTEM_VERSIONING = ON(HISTORY_TABLE = dbo.Products_History, DATA_CONSISTENCY_CHECK = ON));
GO

CREATE TABLE dbo.Orders
(
    OrderID int not null identity primary key,
    OrderDate datetime2 (7) not null
);

CREATE TABLE dbo.OrderLineItems
(
    OrderID int not null,
    ProductID int not null,
    CONSTRAINT FK_OrderLineItems_Orders FOREIGN KEY (OrderID) REFERENCES dbo.Orders (OrderID),
    CONSTRAINT FK_OrderLineItems_Products FOREIGN KEY (ProductID) REFERENCES dbo.Products (ProductID),
    CONSTRAINT PK_OrderLineItems PRIMARY KEY (OrderID, ProductID)
);
GO

-- Load Sample data
insert into Products (Name) values ('a'), ('b');
waitfor delay '00:00:02';
insert into orders (OrderDate) values (getutcdate());
waitfor delay '00:00:02';
update products set name= 'c' where name = 'a'
waitfor delay '00:00:02';
insert into orders (OrderDate) values (getutcdate());
insert into OrderLineItems (OrderID, ProductID) values (1, 1), (1, 2), (2, 1);

我将如何编写一个连接Products到OrderLineItems使用日期的查询Orders？

例如，要查询“包含名称已更改的产品的订单”：

-- Fake syntax:
SELECT o.OrderID, p_then.Name as [Old Name], p_now.Name as [New Name]
FROM dbo.Orders o
INNER JOIN dbo.OrderLineItems oi on o.OrderID = oi.OrderID
INNER JOIN dbo.Products as p_then
    for system time o.OrderDate
    on oi.ProductID = p_then.ProductID
INNER JOIN dbo.Products p_now
--  for system time now
    on oi.ProductID = p_now.ProductID
WHERE p_then.Name <> p_now.Name

Answer 1

您可以使用 检索时态表中的所有历史行FOR SYSTEM_DATE ALL。这允许的手动比较OrderDate的SysStart和SysEnd日期：

SELECT o.OrderID, p_then.Name as [Old Name], p_now.Name as [New Name]
FROM dbo.Orders o
INNER JOIN dbo.OrderLineItems oi on o.OrderID = oi.OrderID
INNER JOIN dbo.Products FOR SYSTEM_TIME ALL as p_then
    on o.OrderDate >= p_then.SysStart and o.OrderDate < p_then.SysEnd
    and oi.ProductID = p_then.ProductID
INNER JOIN dbo.Products p_now
    on oi.ProductID = p_now.ProductID
WHERE p_then.Name <> p_now.Name