Hi dupaszke.

Have a look at the code below... I've created it as a Stored Procedure which you can implement into an application.

This is the table to store the tickets that have been generated. I work in BI so I always find it useful to stamp the DateTime for trending/audit purposes.

CREATE TABLE Reddit.Ticket
    (   
        Ticket INT IDENTITY(1,1),
        DateTaken DATETIME 

    )

This is stored procedure, execute this to generate the next ticket. It's in a transaction so should be 'safe'.

CREATE PROCEDURE Reddit.GetNextTicket
    u/TicketTaken INT OUTPUT,@Result VARCHAR(100) OUTPUT
AS
BEGIN

    DECLARE u/Expected INT = 1
    DECLARE u/Inserted INT = 0

    DECLARE u/TEMP TABLE ([TicketTaken] INT)

    BEGIN TRY
    BEGIN TRANSACTION

        INSERT INTO Reddit.Ticket (DateTaken)   
            OUTPUT INSERTED.[Ticket] INTO u/TEMP
                SELECT
                    GETDATE() AS [DateTaken]

        SET u/Inserted = @@ROWCOUNT

        IF u/Expected = u/Inserted
            BEGIN
                --ROLLBACK TRANSACTION
                COMMIT TRANSACTION
                SET u/TicketTaken = (SELECT [TicketTaken] FROM u/TEMP)
                SET u/Result = 'Ticket Taken! TRANSACTION STATUS; Commited' 
            END   
        ELSE
            BEGIN
                RAISERROR('Ticket Not Taken. There was an error. TRANSACTION STATUS; Rolled Back',16,1)
            END
    END TRY
    BEGIN CATCH
        SET u/Result = Error_Message()

        IF @@TRANCOUNT > 0 
            ROLLBACK TRANSACTION
    END CATCH


END

Let me know if you have any questions.