SQL:waitfor的使用
摘自:http://www.cnblogs.com/downmoon/archive/2010/12/07/1899233.html
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 ]
}
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
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
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
IFOBJECT_ID('dbo.TimeDelay_hh_mm_ss','P') ISNOTNULL
DROPPROCEDURE dbo.TimeDelay_hh_mm_ss;
GO
CREATEPROCEDURE dbo.TimeDelay_hh_mm_ss
(
@DelayLengthchar(8)='00:00:00'
)
AS
DECLARE@ReturnInfovarchar(255)
IFISDATE('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
GO
IFOBJECT_ID('dbo.TimeDelay_hh_mm_ss','P') ISNOTNULL
DROPPROCEDURE dbo.TimeDelay_hh_mm_ss;
GO
CREATEPROCEDURE dbo.TimeDelay_hh_mm_ss
(
@DelayLengthchar(8)='00:00:00'
)
AS
DECLARE@ReturnInfovarchar(255)
IFISDATE('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。
另加例子:
用途有两个:
1、延迟一段时间后执行
比如:
waitfor delay '00:00:05'
print '延迟5秒执行!'
--5秒后执行print
2、指定从何时起执行
比如:
waitfor time '21:17'
print '21:17执行'
--到21:17的时候才会执行print