BEGIN - COMMIT TRANSACTION 的意外、非直觉行为

Question

我写的是我几天前问的this question。

适合我需要的答案是：

UPDATE ProcActivity SET IsActive = 1 WHERE ProcedureName = 'proc_name'
BEGIN TRANSACTION
EXEC proc_name
COMMIT TRANSACTION
UPDATE ProcActivity SET IsActive = 0 WHERE ProcedureName = 'proc_name'

现在这是另一个问题：

直觉上，我以为如果我将UPDATE 语句包装在BEGIN....COMMIT TRANSACTION 中，它会在到达COMMIT... 时立即生效，但我错了。实际上，当你按照上述方式进行操作时，当它到达BEGIN... 时，就会发生更新。

总结一下：

像这样进行更新：

UPDATE ProcActivity SET IsActive = 1 WHERE ProcedureName = 'proc_name'
BEGIN TRANSACTION
EXEC proc_name
COMMIT TRANSACTION
UPDATE ProcActivity SET IsActive = 0 WHERE ProcedureName = 'proc_name'

导致IsActive的值在过程proc_name执行期间被设置为1（更新在过程开始之前生效）。

像这样进行更新：

BEGIN TRANSACTION
UPDATE ProcActivity SET IsActive = 1 WHERE ProcedureName = 'proc_name'
COMMIT TRANSACTION
EXEC proc_name
UPDATE ProcActivity SET IsActive = 0 WHERE ProcedureName = 'proc_name'

在执行proc_name 期间将不起作用。 IsActive 的值在过程执行期间设置为 0。

为什么会这样？其背后的机制是什么？

Answer 1

我无法重现您的问题 - 在这两种情况下，我都会得到 0 - 1 - 0：

IF OBJECT_ID('[dbo].[StackOoverFlow]') IS NOT NULL
BEGIN
    DROP TABLE [dbo].[StackOoverFlow];
END;

IF OBJECT_ID('[dbo].[usp_StackOoverFlow]') IS NOT NULL
BEGIN
    DROP PROCEDURE [dbo].[usp_StackOoverFlow];
END;

GO

CREATE TABLE [dbo].[StackOoverFlow]
(
    [ProcedureName] SYSNAME
   ,[IsActive] BIT
); 

GO

CREATE PROCEDURE [dbo].[usp_StackOoverFlow] AS
BEGIN
    SELECT [IsActive]
    FROM [dbo].[StackOoverFlow]
    WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]';
END;

GO

INSERT INTO [dbo].[StackOoverFlow] ([ProcedureName], [IsActive])
VALUES ('[dbo].[usp_StackOoverFlow]', 0);

GO

SELECT [IsActive]
FROM [dbo].[StackOoverFlow]
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]';

BEGIN TRANSACTION

UPDATE [dbo].[StackOoverFlow]
SET [IsActive] = 1
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]'; 

COMMIT TRANSACTION

EXEC [dbo].[usp_StackOoverFlow];

UPDATE [dbo].[StackOoverFlow]
SET [IsActive] = 0
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]'; 

SELECT [IsActive]
FROM [dbo].[StackOoverFlow]
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]';


GO

SELECT [IsActive]
FROM [dbo].[StackOoverFlow]
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]';

UPDATE [dbo].[StackOoverFlow]
SET [IsActive] = 1
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]'; 

BEGIN TRANSACTION
EXEC [dbo].[usp_StackOoverFlow];
COMMIT TRANSACTION

UPDATE [dbo].[StackOoverFlow]
SET [IsActive] = 0
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]'; 

SELECT [IsActive]
FROM [dbo].[StackOoverFlow]
WHERE [ProcedureName] = '[dbo].[usp_StackOoverFlow]';