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请告知-我在这里缺少什么？临时表 ValidTo 字段不能用作计算列中 UDF 中的参数，而 ValidFrom 确实可以正常工作。

2016 年的 SQL 服务器。

有一个例子。在这种情况下，记录“Masha”必须将 WhenDeleted 标志显示为日期，而不是 null：

GO
DROP FUNCTION IF EXISTS [dbo].[VitalyUTCtoDate];
GO
CREATE FUNCTION [dbo].[VitalyUTCtoDate] (@UTCDate DATETIME2)
RETURNS DATETIME2 WITH SCHEMABINDING AS  
BEGIN 
    RETURN CASE WHEN @UTCDate < '9999-01-01' THEN DATEADD(HOUR, DATEDIFF(HOUR, GETUTCDATE(), GETDATE()), @UTCDate) ELSE NULL END;
END
GO

IF EXISTS(SELECT 1 FROM sys.tables t WHERE t.name = 'VitalyTest')
BEGIN
    EXEC('ALTER TABLE [dbo].[VitalyTest] SET (SYSTEM_VERSIONING = OFF)');
    EXEC('DROP TABLE IF EXISTS [dbo].[VitalyTest]');
    EXEC('DROP TABLE IF EXISTS [dbo].[VitalyTestHistory]');
END
GO
CREATE TABLE [dbo].[VitalyTest](
     [ID] [bigint] IDENTITY(1,1) NOT NULL 
    ,[Name] NVARCHAR(255) NOT NULL
    ,[Value] INT NULL
    ,[ValidFrom] DATETIME2 GENERATED ALWAYS AS ROW START HIDDEN 
    ,[ValidTo] DATETIME2 GENERATED ALWAYS AS ROW END HIDDEN
    ,[WhenCreated] AS dbo.VitalyUTCtoDate(ValidFrom)
    ,[WhenDeleted] AS dbo.VitalyUTCtoDate(ValidTo)
    ,CONSTRAINT [PK_VitalyTest] PRIMARY KEY CLUSTERED ([ID] ASC)
        WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    ,PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo)
)
WITH (SYSTEM_VERSIONING = ON (HISTORY_TABLE = [dbo].[VitalyTestHistory]))
GO

-- Insert Data
INSERT INTO dbo.VitalyTest(Name,Value)VALUES('Vasya',234),('Masha',756);

-- Delete Data
DELETE FROM dbo.VitalyTest WHERE Name = 'Masha';

-- Check resutls
SELECT v.*,v.ValidFrom,v.ValidTo
FROM dbo.VitalyTest FOR SYSTEM_TIME ALL AS v
;

-- Clean-up
GO
IF EXISTS(SELECT 1 FROM sys.tables t WHERE t.name = 'VitalyTest')
BEGIN
    EXEC('ALTER TABLE [dbo].[VitalyTest] SET (SYSTEM_VERSIONING = OFF)');
    EXEC('DROP TABLE IF EXISTS [dbo].[VitalyTest]');
    EXEC('DROP TABLE IF EXISTS [dbo].[VitalyTestHistory]');
END
GO
DROP FUNCTION IF EXISTS [dbo].[VitalyUTCtoDate];
GO

结果

4

1 回答 1

1

我找到了它发生的原因：

  • 时态表存储动作发生之前的数据状态。
  • 即使主表有，临时表历史表也没有任何计算列。
  • 时态表将计算列存储为值（计算值）
  • 当记录即将被删除时WhenDeleted标志在这个阶段仍然是NULL，并且这个NULL在动作之前被记录到历史表中
  • 然后主表中的记录被删除，但是这个 WhenDeleted 计算实际上从未发生过，并且该计算的结果永远不会存储在任何地方
于 2019-01-30T22:37:49.013 回答