Imagine que eu tenha um esquema que inclua Products
, Orders
e OrderLineItems
, Products
sendo uma tabela temporal com versão do sistema.
Esquema:
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);
Como eu escreveria uma consulta que se une Products
ao OrderLineItems
uso da data de Orders
?
Por exemplo, para consultar "Pedidos que contêm produtos cujos nomes foram alterados":
-- 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
Você pode recuperar todas as linhas históricas de uma tabela temporal usando
FOR SYSTEM_DATE ALL
. Isso permite uma comparação manual dasOrderDate
datas eSysStart
:SysEnd