sql-server - DBCC 命令在程序内部不起作用

Question

我有以下查询。从逻辑上讲，过程 usp_mytran 应该将表 dbo.Sales 的 Identity RESEED 为 1。但最后一个查询为 Max_ID_Value 和 Current_Seed_Value 返回不同的值。谁能解释一下为什么 DBCC 命令在程序内不起作用？

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

Answer 1

很抱歉回答我自己的问题。正如 @Kannan Kandasamy 所指出的，正是 ROLLBACK TRANSACTION 代码恢复了 DBCC CHECKIDENT 完成的工作。因此，为了使其正常工作，我创建了一个名为 Reseed_Sales 的作业，其中包含表 dbo.Sales 的 RESEED Identity 代码。以下是过程 usp_mytran 的最终查询。

--  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