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 table dbo.Sales 的身份重新设置为 1。但是最后一个查询为 Max_ID_Value 和 Current_Seed_Value 返回了不同的值。谁能解释为什么 DBCC 命令在程序内部不起作用？

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

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

如果你检查 ident_current 现在它显示 2 而在下一个运行它显示 4 等等因为 ROLLBACK TRANSACTION

现在多次执行后检查"EXEC usp_mytran"

select IDENT_CURRENT('test.dbo.Sales')

您会看到 checkident 不会重置。

如果我们删除该事务，则 CHECKIDENT 将重新设定为 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

现在多次执行后检查"EXEC usp_mytran"

select IDENT_CURRENT('test.dbo.Sales')

您将看到补种值为“1”

同时检查以下示例...

Can we rollback to original state after we have used DBCC CHECKIDENT to restart Identity column count?

Answer 2

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 所做的工作。所以为了让它工作，我创建了一个名为 Reseed_Sales 的作业，其中包含用于 table dbo.Sales 的 RESEED Identity 的代码。下面是程序 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

DBCC 命令在程序内部不起作用

DBCC Command Not Working Inside Procedure

tsql

sql-server

stored-procedures

dbcc