2

I have below query. Logically, the procedure usp_mytran should RESEED the Identity to 1 for table dbo.Sales. But the last query is returning different values for Max_ID_Value and Current_Seed_Value. Can anyone please explain why DBCC command is not working inside procedure?

USE tempdb

--  Create table 
CREATE  TABLE dbo.Sales
(ID INT IDENTITY(1,1), Address VARCHAR(200))
GO

--  Procedure to Populate data into dbo.Sales
CREATE PROCEDURE usp_mytran 
AS
BEGIN
BEGIN TRANSACTION
    INSERT dbo.Sales
            ( Address )
    VALUES  ( 'Dwarka, Delhi' );

    --  Delete it for some reason
    DELETE FROM dbo.Sales;

    --  Code to check max ID value, and verify it again IDENTITY SEED
    DECLARE @MaxValue INT = (SELECT ISNULL(MAX(ID),1) FROM dbo.Sales)
    IF @MaxValue IS NOT NULL AND @MaxValue <> IDENT_CURRENT('dbo.Sales')
        DBCC CHECKIDENT ( 'tempdb.dbo.Sales', RESEED, @MaxValue );
ROLLBACK TRANSACTION
END

--  Ideally, this should RESEED the Identity of dbo.Sales table.
EXEC usp_mytran

--  Max_ID_Value & Current_Seed_Value should be same
SELECT ISNULL(MAX(ID),1) AS Max_ID_Value, IDENT_CURRENT('dbo.Sales') AS Current_Seed_Value FROM dbo.Sales
4

2 回答 2

3

很抱歉回答我自己的问题。正如@Kannan Kandasamy 所指出的，它ROLLBACK TRANSACTION是恢复由DBCC CHECKIDENT. 因此，为了使其工作，我创建了一个名称Reseed_Sales包含代码的作业 RESEED Identity for table dbo.Sales。以下是 procedure 的最终查询usp_mytran。

--  Procedure to Populate data into dbo.Sales
ALTER PROCEDURE usp_mytran 
AS
BEGIN
BEGIN TRANSACTION
    INSERT dbo.Sales
            ( Address )
    VALUES  ( 'Dwarka, Delhi' );

    --  Delete it for some reason
    DELETE FROM dbo.Sales;

    --  Code to check max ID value, and verify it again IDENTITY SEED
    DECLARE @MaxValue INT = (SELECT ISNULL(MAX(ID),1) FROM dbo.Sales)
    IF @MaxValue IS NOT NULL AND @MaxValue <> IDENT_CURRENT('dbo.Sales')
        EXEC msdb..sp_start_job @job_name = 'Reseed_Sales'
ROLLBACK TRANSACTION
END
于 2016-10-15T13:23:45.510 回答
1

实际上它在存储过程中按预期工作： Rollback tran 将回滚 checkident 值 - 这就是代码中发生的事情

--  Procedure to Populate data into dbo.Sales
alter PROCEDURE usp_mytran 
AS
BEGIN
    BEGIN TRANSACTION
    INSERT dbo.Sales
            ( Address )
    VALUES  ( 'Dwarka, Delhi' );

    --  Delete it for some reason
    DELETE FROM dbo.Sales;

    --  Code to check max ID value, and verify it again IDENTITY SEED
    DECLARE @MaxValue INT = (SELECT ISNULL(MAX(ID),1) FROM dbo.Sales)
    IF @MaxValue IS NOT NULL AND @MaxValue <> IDENT_CURRENT('test.dbo.Sales')
        DBCC CHECKIDENT ( 'test.dbo.Sales', RESEED, @MaxValue );
    ROLLBACK TRANSACTION
END

如果您现在检查 ident_current 它显示 2 并且在下一次运行时它显示 4 等等，因为ROLLBACK TRANSACTION

现在检查多次执行“EXEC usp_mytran”

select IDENT_CURRENT('test.dbo.Sales')

您将看到 checkident 不会重置。

如果我们删除该事务，则 CHECKIDENT 将重新设置为 1。

下方评论交易

--  Procedure to Populate data into dbo.Sales
alter PROCEDURE usp_mytran 
AS
BEGIN
    --BEGIN TRANSACTION
    INSERT dbo.Sales
            ( Address )
    VALUES  ( 'Dwarka, Delhi' );

    --  Delete it for some reason
    DELETE FROM dbo.Sales;

    --  Code to check max ID value, and verify it again IDENTITY SEED
    DECLARE @MaxValue INT = (SELECT ISNULL(MAX(ID),1) FROM dbo.Sales)
    IF @MaxValue IS NOT NULL AND @MaxValue <> IDENT_CURRENT('test.dbo.Sales')
        DBCC CHECKIDENT ( 'test.dbo.Sales', RESEED, @MaxValue );
    --ROLLBACK TRANSACTION
END

现在检查多次执行“EXEC usp_mytran”

select IDENT_CURRENT('test.dbo.Sales')

您将看到重新种子值为“1”

检查以下示例...

使用 DBCC CHECKIDENT 重新启动 Identity 列计数后，我们可以回滚到原始状态吗？

于 2016-10-15T13:13:16.700 回答