sql - Data did not display in Stored Procedure -

i'm new here, please correct me if ask wrongly.

i did stored procedure, however, when execute it, errornumber, spname , errormessage came out.

can please explain me did wrong? thanks.

this executed:

exec dbo.sppartmasterextension @domainsite = 'bris0011', @itemno='1002424251911',                                @itemdescription = 'new item', @itemvalue = '1',                                @itemum = '1', @employeeno = 'nn031097' 

this stored procedure:

create procedure [dbo].[sppartmasterextension]    @domainsite nvarchar(8),    @itemno nvarchar(18),    @itemdescription nvarchar(50),    @itemvalue nvarchar(50),    @itemum nvarchar(50),    @employeeno nvarchar(18) begin    declare @errorno integer = '',            @spname nvarchar(max) = '',            @errormessage nvarchar(max) = ''   declare @itemumoriginal nvarchar(50)    if exists (select id partmasterextension               itemno = @itemno , itemdescription = @itemdescription , domainsite =@domainsite)   begin       update partmasterextension        set itemvalue = @itemvalue,            itemum = @itemum,           datetimestamp = getdate(),           employeeno = @employeeno                   itemno = @itemno , itemdescription = @itemdescription , domainsite = @domainsite    end   else    begin     begin try         insert partmasterextension            select                 @domainsite, @itemno, @itemdescription,                @itemvalue, @itemum, getdate(), @employeeno     end try     begin catch          select              @errorno = error_number(),             @spname = error_procedure(),             @errormessage = error_message();     end catch   end    select      @errorno errornumber,     @spname spname,      @errormessage errormessage; end go 

if product exist, update process , then, last select. if data doesn't exist, try inserting and, if error occurs, set values variables declared, before returning it.

what expecting stored procedure?