更改系统版本控制表（临时表）列的最佳机制？

Question

我有一个系统版本控制表，其历史表相关如下：

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，我想在系统版本表和历史记录中更改“LineCode”的数据类型。修改后再次启用如下：

--- 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])   
);   

但我收到以下错误：

当未定义 SYSTEM_TIME 时间段时，无法将 SYSTEM_VERSIONING 设置为 ON。

我该如何解决这个问题。

Answer 1

根据您的问题，您是说ExpenseCenter_archive 是ExpenseCenter..的临时表，但错误消息显示

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，我会按照其他的表格制作一个临时表..

如果它用于新表..

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 recommends doing it in a transaction..

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 ;  

如果我想将现有的表设为 Temporal，那么我会在下面这样做

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)

现在终于将时间设置为 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

alter system versioning table 不需要设置SYSTEM_VERSIONING = OFF，直接使用ALTER TABLE ...