Routine needs Streamlining

[Jim Sawyer]

I am using the following routine in Delphi/FireDAC. The RECORDS table has about 3 million records and the routine takes way too much time to be practical. I'm sure it can be streamlined using JOIN, but I can't figure out how to do it. I would like very much if someone can give me some pointers that I can use.

The routine is:

// patient
pQuery := TFDQuery.Create( AConnection );
with pQuery do
begin
Connection := AConnection;
SQL.Add( 'Select Patno, TargSel from Patient where TargSel = true' );
Open;
while not EOF do
begin
// targservice
tsQuery := TFDQuery.Create( AConnection );
with tsQuery do
begin
Connection := AConnection;
SQL.Add( 'Select * from TargService where Targno = :T and AllIn = true' );
ParamByName('T').AsInteger := HotTargno;
Open;
while not EOF do
begin
// records
lAllIn := true;
rQuery := TFDQuery.Create( AConnection );
with rQuery do
begin
Connection := AConnection;
SQL.Add( 'Select Servno from Records where Servno = :S and SSDO = true and RecDate between :St and :E' );
ParamByName('S').AsInteger := tsQuery.FieldValues['Servno'];
ParamByName('St').AsDate := dStart;
ParamByName('E').AsDate := dEnd;
IndexFieldNames := 'Servno';
IndexesActive := true;
Open;
if EOF then
lAllIn := false;
end;
Next;
if not lAllIn then
Break;
end;
if not lAllIn then
AConnection.ExecSQL( 'Update Patient set TargSel = false where Patno = :P',
[pQuery.FieldValues['Patno']] );
end;
Next;
end;
Free;
end;

Thank you.
Jim Sawyer