SQL Server 2008中SQL之WaitFor-在规定时间执行操作

    

 

 

在SQL Server 2005以上版本中，在一个增强的WaitFor命令，其作用可以和一个job相当。但使用更加简捷。

看MSDN:
http://msdn.microsoft.com/zh-cn/library/ms187331.aspx
语法为：

WAITFOR
{
DELAY 'time_to_pass'
| TIME 'time_to_execute'
| [ ( receive_statement ) | ( get_conversation_group_statement ) ]
[ , TIMEOUT timeout ]
}

WAITFOR { DELAY 'time_to_pass' | TIME 'time_to_execute' | [ ( receive_statement ) | ( get_conversation_group_statement ) ] [ , TIMEOUT timeout ] }

以下示例在晚上 10:20 (22:20 ) 执行存储过程 sp_update_job 。

USE msdb;
EXECUTE sp_add_job @job_name ='TestJob';
BEGIN
WAITFOR TIME '22:20';
EXECUTE sp_update_job @job_name ='TestJob',
@new_name ='UpdatedJob';
END;
GO

USE msdb; EXECUTE sp_add_job @job_name = 'TestJob'; BEGIN WAITFOR TIME '22:20'; EXECUTE sp_update_job @job_name = 'TestJob', @new_name = 'UpdatedJob'; END; GO

以下示例在两小时的延迟后执行存储过程。注意:Delay最多不超过24小时

BEGIN
WAITFOR DELAY '02:00';
EXECUTE sp_helpdb;
END;
GO
以下示例显示如何对 WAITFOR DELAY选项使用局部变量。将创建一个存储过程，该过程将等待可变的时间段，然后将经过的小时、分钟和秒数信息返回给用户。
USE AdventureWorks2008R2;
GO
IF OBJECT_ID('dbo.TimeDelay_hh_mm_ss','P') IS NOT NULL
DROP PROCEDURE dbo.TimeDelay_hh_mm_ss;
GO
CREATE PROCEDURE dbo.TimeDelay_hh_mm_ss
(
@DelayLength char(8)='00:00:00'
)
AS
DECLARE @ReturnInfo varchar(255)
IF ISDATE('2000-01-01 ' +@DelayLength +'.000') = 0
BEGIN
SELECT @ReturnInfo ='Invalid time ' +@DelayLength
+ ',hh:mm:ss, submitted.';
-- This PRINT statement is for testing,not usein production.
PRINT @ReturnInfo
RETURN(1)
END
BEGIN
WAITFOR DELAY @DelayLength
SELECT @ReturnInfo ='A total time of ' +@DelayLength + ',
hh:mm:ss, has elapsed! Your time is up.'
-- This PRINT statement is for testing,not usein production.
PRINT @ReturnInfo;
END;
GO
/* This statement executes the dbo.TimeDelay_hh_mm_ss procedure. */
EXEC TimeDelay_hh_mm_ss '00:00:10';
GO

BEGIN WAITFOR DELAY '02:00'; EXECUTE sp_helpdb; END; GO 以下示例显示如何对 WAITFOR DELAY选项使用局部变量。将创建一个存储过程，该过程将等待可变的时间段，然后将经过的小时、分钟和秒数信息返回给用户。 USE AdventureWorks2008R2; GO IF OBJECT_ID('dbo.TimeDelay_hh_mm_ss','P') IS NOT NULL DROP PROCEDURE dbo.TimeDelay_hh_mm_ss; GO CREATE PROCEDURE dbo.TimeDelay_hh_mm_ss ( @DelayLength char(8)= '00:00:00' ) AS DECLARE @ReturnInfo varchar(255) IF ISDATE('2000-01-01 ' + @DelayLength + '.000') = 0 BEGIN SELECT @ReturnInfo = 'Invalid time ' + @DelayLength + ',hh:mm:ss, submitted.'; -- This PRINT statement is for testing, not use in production. PRINT @ReturnInfo RETURN(1) END BEGIN WAITFOR DELAY @DelayLength SELECT @ReturnInfo = 'A total time of ' + @DelayLength + ', hh:mm:ss, has elapsed! Your time is up.' -- This PRINT statement is for testing, not use in production. PRINT @ReturnInfo; END; GO /* This statement executes the dbo.TimeDelay_hh_mm_ss procedure. */ EXEC TimeDelay_hh_mm_ss '00:00:10'; GO


执行结果：

A total time of 00:00:10, in hh:mm:ss, has elapsed.Your time is up.

小结：这是一种轻巧的解决方案。当你没有权限指定job时，可以考虑用WaitFor语句。

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