DELAY

Is the specified period of time that must pass, up to a maximum of 24 hours, before execution of a batch, stored procedure, or transaction proceeds.

' time_to_pass '

Is the period of time to wait. time_to_pass can be specified in one of the acceptable formats for datetime data, or it can be specified as a local variable. Dates cannot be specified; therefore, the date part of the datetime value is not allowed.

TIME

Is the specified time when the batch, stored procedure, or transaction runs.

' time_to_execute '

Is the time at which the WAITFOR statement finishes. time_to_execute can be specified in one of the acceptable formats for datetime data, or it can be specified as a local variable. Dates cannot be specified; therefore, the date part of the datetime value is not allowed.

receive_statement

Is a valid RECEIVE statement.

Important:
WAITFOR with a receive_statement is applicable only to Service Broker messages. For more information, see RECEIVE (Transact-SQL).

get_conversation_group_statement

Is a valid GET CONVERSATION GROUP statement.

Important:
WAITFOR with a get_conversation_group_statement is applicable only to Service Broker messages. For more information, see GET CONVERSATION GROUP (Transact-SQL).

TIMEOUT timeout

Specifies the period of time, in milliseconds, to wait for a message to arrive on the queue.

Important:
Specifying WAITFOR with TIMEOUT is applicable only to Service Broker messages. For more information, see RECEIVE (Transact-SQL) and GET CONVERSATION GROUP (Transact-SQL).

While executing the WAITFOR statement, the transaction is running and no other requests can run under the same transaction.

The actual time delay may vary from the time specified in time_to_pass, time_to_execute, or timeout and depends on the activity level of the server. The time counter starts when the thread associated with the WAITFOR statement is scheduled. If the server is busy, the thread may not be immediately scheduled; therefore, the time delay may be longer than the specified time.

WAITFOR does not change the semantics of a query. If a query cannot return any rows, WAITFOR will wait forever or until TIMEOUT is reached, if specified.

Cursors cannot be opened on WAITFOR statements.

Views cannot be defined on WAITFOR statements.

When the query exceeds the query wait option, the WAITFOR statement argument can complete without running. For more information about the configuration option, see query wait Option. To see the active and waiting processes, use sp_who.

Each WAITFOR statement has a thread associated with it. If many WAITFOR statements are specified on the same server, many threads can be tied up waiting for these statements to run. SQL Server monitors the number of threads associated with WAITFOR statements, and randomly selects some of these threads to exit if the server starts to experience thread starvation.

You can create a deadlock by running a query with WAITFOR within a transaction that also holds locks preventing changes to the rowset that the WAITFOR statement is trying to access. SQL Server identifies these scenarios and returns an empty result set if the chance of such a deadlock exists.

A. Using WAITFOR TIME

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

B. Using WAITFOR DELAY

BEGIN
    WAITFOR DELAY '02:00';
    EXECUTE sp_helpdb;
END;
GO

C. Using WAITFOR DELAY with a local variable

USE AdventureWorks;
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

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

Reference

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