Raiserror Nowait SQL Server - SQL

Introduction

In SQL Server, the raiserror function is used to raise an error message and return it to the application. By default, when raiserror is executed, the application is blocked until the error message is returned. However, in some cases, it may be desirable to raise an error message without blocking the application. This is where the nowait option in raiserror comes in.

Syntax

The syntax for raiserror with the nowait option is as follows:

RAISERROR ( { msg_id | msg_str } { , severity , state }  
    [ , argument [ ,...n ] ] ) [ WITH NOWAIT ]

The nowait option is specified using the WITH NOWAIT clause at the end of the statement.

Example

Suppose we have a stored procedure that performs a long-running task and we want to provide regular updates to the application while the task is running. We could use raiserror with the nowait option to accomplish this.

CREATE PROCEDURE long_running_task
AS
BEGIN
    SET NOCOUNT ON;
    
    DECLARE @i INT = 0;
    
    WHILE (@i < 10)
    BEGIN
        SET @i = @i + 1;
        WAITFOR DELAY '00:00:01';
        RAISERROR ('Task is %d%% complete', 0, 1, (@i * 10)) WITH NOWAIT;
    END
    
    SELECT 'Task complete';
END

In this example, the stored procedure performs a long-running task that takes 10 seconds to complete. During each iteration of the loop, the raiserror function is called with the nowait option to provide an update to the application. The update indicates the percentage complete of the task.

Conclusion

The raiserror function with the nowait option allows SQL Server developers to raise error messages without blocking the application. This can be useful in scenarios where the application needs to know the progress of a long-running task. By using raiserror with the nowait option, developers can provide regular updates to the application while the task is running.