🚀 go-pugleaf

Mark Stephens <marks@stconsult.co.nz> wrote in article
<01bd8792$dfb1fa40$081260cb@actrix.gen.nz.actrix.gen.nz>...
> Hi. I have a fairly complex application that is currently two-tier, ie
> database sits on a server and the client application talks to it through
> BDE on the client.
> 
> I want to move the application to a 3-tier structure, and I've examined
the
> sample Delphi programs in some depth and tried to delve my way through
the
> on-line help about COM, multi-tier and all that. I understand the
> principles but I still don't understand the technicalities of it.
> 
> I have some questions about it:
> 1. My application currently dynamically constructs SQL code into TQuery
> objects, where the tables, selection criteria and sort order are all
> potentially dynamic. How can I do this using TClientDataSet - it appears
to
> have no way to send SQL to the data broker?
> 2. How do you create the server so it is registered? I tried creating a
> server, created a few datasets, a provider etc, all as on the sample, but
I
> couldn't find out how to create the text library that appears to be
> automatically generated in the sample.
> 
> Are there any further resources out there about how to construct 3-tier
> database structures - it would seem to me the demand for such
applications
> is going to dramatically increase in the not too distant future, and
> there's not much information about how to do it.
> 

No kidding there isn't much information on it! We found that out soon
enough. However, now that I know what I do, looking back in the D3 help
pages, it is all explained - just not in layman's terms.
There is an example on how to set up the application server (do a search in
the help under 'Application Server'). The server is registered when you
execute it for the first time.
The client sends the SQL, via the TRemoteServer (or TMidasConnection) to a
TQuery object on the server. This TQuery is 'made visible' to the client
(that's the simplest way to explain it) - how to make it visible is
explained in the help. The TRemoteServer has a property call AppServer
which points to this interface.

Once you have the architecture in place, it's all pretty simple.
Good luck - you may need it :-)

- Graeme Vincent