On Nov 4, 2011, at 12:05 PM, Steve Teale wrote: > On Fri, 04 Nov 2011 10:19:23 -0700, bls wrote: > >> On 11/04/2011 09:25 AM, Steve Teale wrote: >>> I don't think you need to worry >>> about changes while stepping through rows. >> > > As in don't worry about something over which you have no control! > >> However, there are always many ways to skin a cat. PostgreSQL, Firebird, >> MSSQL Server (not sure about MySQL) enable you to trigger server side >> events. >> Means the database server fires an update event (say employee deleted >> event) and a D function living in a secondary thread will catch this >> event and inform all interested parties (subscribers**) to refresh their >> RowSet. (and of course the UI) >> >> Beside, this is the way we create mission critical,db-centric realtime >> apps. works fine. >> My 2 cents. > > Bjoern > > There's not a hint of that in the MySQL protocol. It'a purely command/ > response. The commands are: ... > I don't see a 'let me know when something happens' command here. There is > also no trace of it in the C API.
Unless something has changed in the last few years, the way to do this in MSSQL is via a plugin in the SQL server itself. Back in the days of yore this was via extended stored procedures, which were loaded as a DLL by the SQL server, but I think more recent iterations can call COM or .NET code or something like that as well. In short, the event notification isn't typically done via a back-feed through a client connection. Do any modern DBMSes have pub/sub functionality like this?
