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DCOM-paramatized queries

Posted on 2000-04-05
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Last Modified: 2012-05-04
Hi All,

How do I return the result set of a paramatised query in a RemoteDataModule to a DCOM client.

For standard SELECT queries I just attach a TProvider and export it, but if I need to do a SELECT * WHERE FIELD1 = :PARAM1 OR FIELD2 = :PARAM2 what do I need to do?

Code samples will be appreciated.

Thanx,
Gavin

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Question by:ShadowFax
  • 2
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5 Comments
 
LVL 13

Expert Comment

by:Epsylon
ID: 2687608
You need to add a new method or some new properties (one for each parameter) to the server module. I would prefer to create a method. Use the type library to add this new method.

When you want to do a new query, the client calls the method with new parameters. In the method, which is running on the server, the actual query has to be done.


Client:

DCOMConnection.Appserver.DoQuery(param1, param2);


Server:

procedure TXXXXX.DoQuery(param1: Integer; const Param2: WideString);
begin
  Query1.Active := false;
  <change query parameters>
  Query1.Active := true;
end;


Regards,

Epsylon.
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LVL 2

Expert Comment

by:kubeerja
ID: 2688365
you can send the whole select string from the client with the parameters like this :

procedure TForm1.SpeedButton1Click(Sender: TObject);
var
  StrSql : OleVariant ;
begin
     StrSql := Memo1.Text ;
      with DM.ClientDataSet2 do
       begin
          Data := Provider.DataRequest(StrSql) ;
       end ;
end;

in the server side do the following :

function TMysrv.Provider2DataRequest(Sender: TObject;
  Input: OleVariant): OleVariant;
begin
     Provider2.DataSet.Close ;
     // Provider1 needs to casted to TQuery type
     // since DataSet in TProvider doesn't support SQL
     TQuery(Provider2.DataSet).SQL.Clear ;
     TQuery(Provider2.DataSet).SQL.Add(Input) ;
     Provider2.DataSet.Open ;
     Result := Provider2.Data ;
end;
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Author Comment

by:ShadowFax
ID: 2689164
Thanx for your responses, after I'd asked the question I worked it out.

Your posts confirmed my attempts.

Both ways work, so who gets the points Epsylon/kubeerja?
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LVL 13

Accepted Solution

by:
Epsylon earned 300 total points
ID: 2690212
The one who is first   :o)
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Author Comment

by:ShadowFax
ID: 2690252
Early worm catches the bird!!!

.....or points in this case, thanx guys for replying.
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