At 09:10 AM 4/08/2007, you wrote:

>Hi all,
> I'd like to dynamically change the SQL of my Master & Detail
>TIBOQuerys (used to interface to FreeReport 2.34 components),but I get
>an error complaining that the Detail query can no-longer find the
>fields from the first SQL query it used when it was first opened. How
>can I tell it to forget about the first query's fields?
>
>IBOQuery2->Datasource = Datasource1.
>I start with this (via a button)...
>
> IBOQuery1->Close();
> IBOQuery1->Unprepare();
> IBOQuery1->SQL->Clear();
> IBOQuery1->SQL->Add("SELECT CAT1NO, CAT1 FROM CATEGORY1 where
>DEPT='EWS'");
> IBOQuery1->Prepare();
> IBOQuery1->Open();
>
> IBOQuery2->Close();
> IBOQuery2->Unprepare();
> IBOQuery2->SQL->Clear();
> IBOQuery2->SQL->Add("SELECT CAT2NO, CAT2 FROM CATEGORY2 where
>CAT1NO=:CAT1NO");
> IBOQuery2->Prepare();
> IBOQuery2->Open();
>
>and all is good. Then ...
>
> IBOQuery1->Close();
> IBOQuery1->Unprepare();
> IBOQuery1->SQL->Clear();
> IBOQuery1->SQL->Add("select CAT2NO,CAT1NO,CAT2 from CATEGORY2 where
>CAT1NO < 200");
> IBOQuery1->Prepare();
> IBOQuery1->Open();
>
> IBOQuery2->Close();
> IBOQuery2->Unprepare();
> IBOQuery2->SQL->Clear();
> IBOQuery2->SQL->Add("select CAT3 from CATEGORY3 where CAT2NO=:CAT2NO");
> IBOQuery2->Prepare();
> IBOQuery2->Open();
>
>give the error that "IBOQuery2: Field 'CAT2NO' not found."
>
>If I start with the later SQL pair first, then it complains that
>IBOQuery2: CAT3 can't be found.

The order of doing things is wrong here; and an important step is
missing (nil out the detail's Datasource property).

Try this (sorry about the Pascal):

procedure SwapSQL (NewSql1, NewSql2: string; NewDS:TDatasource);
begin
if IBOQuery2.Active then
IBOQuery2.Close;
IBOQuery2.SQL.Clear; // this causes Unprepare
IBOQuery2.Datasource := Nil; // ESSENTIAL!!

if IBOQuery1.Active then
IBOQuery1.Close;
IBOQuery1.SQL.Clear; // this causes Unprepare

// Now we are clean so we set up the new structure
IBOQuery1.Sql.Add(NewSql1);
IBOQuery2.Sql.Add(NewSql2);
IBOQuery2.Datasource := NewDS;

// No need to call Prepare, as Open calls it

// Include some try..except protection here
....
IBOQuery1.Open;
IBOQuery2.Open;
....
end;

On your buttonclick:

....

var
sql1, sql2: String;
DS: TDatasource;
begin
//SelectedMaster is a string property you have set up
if SelectedMaster = 'CATEGORY1' then
begin
sql1 := 'SELECT CAT1NO, CAT1 FROM CATEGORY1
where DEPT='EWS';
sql2 := 'select CAT3 from CATEGORY3
where CAT2NO=:CAT2NO
DS := dsCategory1;
end
else
if SelectedMaster = ...............
...
end;
SwapSQL (sql1, sql2, DS);
end;

Helen