JETZT FÜR SYSTEMZEIT MIT Spalte als effektive Systemzeit

Stellen Sie sich vor mir ein Schema habe , das umfasst Products, Ordersund OrderLineItemsmit Productseinem System-versioniert zeitlichen Tisch zu sein.

Schema:

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);

Wie würde ich eine Abfrage schreiben Products, OrderLineItemsdie das Datum von verwendet Orders?

Zum Beispiel, um "Bestellungen abzufragen, die Produkte enthalten, deren Namen sich geändert haben":

-- 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

Mit können Sie alle historischen Zeilen aus einer Zeittabelle abrufen FOR SYSTEM_DATE ALL. Das erlaubt einen manuellen Vergleich der OrderDateauf die SysStartund SysEndTermine:

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