想象一下,我有一个包含Products
、Orders
和的模式OrderLineItems
,它Products
是一个系统版本化的时态表。
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);
我将如何编写一个查询Products
来OrderLineItems
使用日期从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
您可以使用
FOR SYSTEM_DATE ALL
. 这允许手动比较OrderDate
到SysStart
和SysEnd
日期: