更改系统版本表（临时表）列的最佳机制？

Question

我有一个与历史表相关的系统版本表，如下所示：

CREATE TABLE [dbo].[ExpenseCenter_Archive](
    [ExpenseCenterId] [tinyint] NOT NULL,
    [Name] [nvarchar](200) NOT NULL,
    [LineCode] [smallint] NOT NULL,
    [SysStartTime] [datetime2](2) NOT NULL,
    [SysEndTime] [datetime2](2) NOT NULL
) ON [FG_HISTORY]
GO
-------
CREATE TABLE [dbo].[ExpenseCenter](
    [ExpenseCenterId] [tinyint] NOT NULL,
    [Name] [nvarchar](200) NOT NULL,
    [LineCode] [smallint] NOT NULL,
    [SysStartTime] [datetime2](2) GENERATED ALWAYS AS ROW START NOT NULL,
    [SysEndTime] [datetime2](2) GENERATED ALWAYS AS ROW END NOT NULL,
 CONSTRAINT [PK_ExpenseCenter] PRIMARY KEY CLUSTERED 
(
    [ExpenseCenterId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [FG_DATA],
CONSTRAINT [UK_ExpenseCenterName] UNIQUE NONCLUSTERED 
(
    [Name] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [FG_INDEX],
    PERIOD FOR SYSTEM_TIME ([SysStartTime], [SysEndTime])
) ON [FG_DATA]
WITH
(
SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[ExpenseCenter_Archive] , DATA_CONSISTENCY_CHECK = ON )
)
GO

现在，我想更改系统版本表和历史记录中“ LineCode”的数据类型。更改后再次启用它，如下所示：

--- Before edit column
ALTER TABLE [dbo].[ExpenseCenter] SET (SYSTEM_VERSIONING = OFF);  
-- ## Edit column in ssms ##

--- After edit column
ALTER TABLE [dbo].[ExpenseCenter] 
SET    
(   
SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[ExpenseCenter_Archive])   
);   

但是我收到以下错误：

如果未定义SYSTEM_TIME周期，则无法将SYSTEM_VERSIONING设置为ON。

我该如何解决这个问题。

Answer 1

从你的问题来看，你是说这ExpenseCenter_archive是ExpenseCenter..的时态表，但错误消息说

你没有系统版本表[dbo].[ExpenseCenter]，如果你想要系统版本表，添加 system_time 到它

所以这里是步骤，我将遵循制作其他表格的临时表..

如果是新桌子..

CREATE TABLE Department   
(    
     DeptID int NOT NULL PRIMARY KEY CLUSTERED  
   , DeptName varchar(50) NOT NULL  
   , ManagerID INT  NULL  
   , ParentDeptID int NULL  
   , SysStartTime datetime2 GENERATED ALWAYS AS ROW START NOT NULL  
   , SysEndTime datetime2 GENERATED ALWAYS AS ROW END NOT NULL  
   , PERIOD FOR SYSTEM_TIME (SysStartTime,SysEndTime)     
)    
WITH (SYSTEM_VERSIONING = ON)   
;  

如果我需要更改这个新创建的表的数据类型..

MSDN 建议在事务中进行..

BEGIN TRAN   
ALTER TABLE [dbo].[CompanyLocation] SET (SYSTEM_VERSIONING = OFF);  

ALTER TABLE [CompanyLocation] ADD Cntr INT IDENTITY (1,1);   

ALTER TABLE [dbo].[CompanyLocation]    
SET    
(   
SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[CompanyLocationHistory])   
);   
COMMIT ;  

如果我想制作一个现有的临时表，那么我会在下面做

ALTER TABLE dbo.Product
ADD StartTime DATETIME2 GENERATED ALWAYS AS ROW START
  HIDDEN DEFAULT GETUTCDATE(),
 EndTime  DATETIME2 GENERATED ALWAYS AS ROW END
  HIDDEN DEFAULT
     CONVERT(DATETIME2, '9999-12-31 23:59:59.9999999'),
 PERIOD FOR SYSTEM_TIME (StartTime, EndTime)

现在终于设置了 Temporal ON

ALTER TABLE dbo.Product
SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE=dbo.ProductHistory))
GO

参考资料：
http : //sqlhints.com/tag/modify-existing-table-as-system-versioned-temporal-table/
https://msdn.microsoft.com/en-us/library/mt590957.aspx

Answer 2

对于更改系统版本控制表，您不需要设置SYSTEM_VERSIONING = OFF，而是直接使用ALTER TABLE ...