Merge two Firebird databases from Delphi - delphi

Question

I'm using the Delphi Sydney version and the database is Firebird 2.5.
I have two databases with identical structures, but it's not 100% the same data.
My strategy is to create two FDConnections and two FDQueries, but I don't know how to get data from one table and insert it into another without creating a TYPE and complete structure for every table and sending every field. Datasource/FDTable?
procedure TForm1.Button2Click(Sender: TObject);
begin
Memo1.Lines.Clear;
DM_Data.FDQryDatabase.Close;
DM_Data.FDQryDatabase.SQL.Clear;
DM_Data.FDQryDatabase.SQL.Add('SELECT * FROM DOCUMENTI_FAMIGLIA');
DM_Data.FDQryDatabase.Open;
while not(DM_Data.FDQryDatabase.Eof) do
begin
Memo1.Lines.Add(DM_Data.FDQryDatabase.FieldValues['FDOC_IDFAMIGLIA']);
DM_Data.FDQryDatabase.Next;
end;
Memo1.Lines.Add('--------------------');
DM_Data.FDQuerySource.Close;
DM_Data.FDQuerySource.SQL.Clear;
DM_Data.FDQuerySource.SQL.Add('SELECT * FROM DOCUMENTI_FAMIGLIA');
DM_Data.FDQuerySource.Open;
while not(DM_Data.FDQuerySource.Eof) do
begin
Memo1.Lines.Add(DM_Data.FDQuerySource.FieldValues['FDOC_IDFAMIGLIA']);
// Insert
DM_Data.FDQuerySource.Next;
end;
end;
I would like to know how to migrate from one database to another using Delphi objects making a shorter solution. FDQryDatabase will be the primary database, FDQuerySource will be added to FDQryDatabase. I don't have a problem doing table-by-table.
Some tables have 17 thousand of data; I will need to include them without duplicate data and this process runs every day until the system migrates to another (I don't know when).

Answer 1

You can add a flag to know what you already move :
procedure TForm1.Button1Click(Sender: TObject);
var
LList: TList<string>;
i: integer;
begin
LList := TList<string>.Create;
try
FDQryDatabase.Close;
FDQryDatabase.SQL.Clear;
FDQryDatabase.SQL.Add('SELECT * FROM DOCUMENTI_FAMIGLIA');
FDQryDatabase.Open;
while not FDQryDatabase.Eof do
begin
LList.Add(FDQryDatabase.FieldValues['FDOC_IDFAMIGLIA']);
FDQryDatabase.Next;
end;
FDQuerySource.SQL.Clear;
for i := 0 to LList.Count - 1 do
begin
if i mod 500 = 0 then
begin
FDQuerySource.ExecSQL;
FDQuerySource.SQL.Clear;
end;
FDQuerySource.SQL.Add('INSERT INTO DOCUMENTI_FAMIGLIA (FDOC_IDFAMIGLIA)');
FDQuerySource.SQL.Add(' SELECT ' + LList.Items[i]);
FDQuerySource.SQL.Add(' FROM DOCUMENTI_FAMIGLIA');
FDQuerySource.SQL.Add(' WHERE NOT EXISTS (SELECT 1 FROM DOCUMENTI_FAMIGLIA df WHERE df.FDOC_IDFAMIGLIA = ' + LList.Items[i] + ');');
end;
if FDQuerySource.SQL.Count > 0 then
FDQuerySource.ExecSQL;
finally
FDQryDatabase.Close;
FreeAndNil(LList);
end;
end;