Artigos Delphi Auto completar edit ou dbedit
Var

Aux : Integer;

Posicao : Integer;

begin

        Try

        Query1.Active := False;

        Query1.SQL.Clear;

        If Edit1.Text <> '' then

        begin
Query1.SQL.Add('SELECT * FROM TABELA WHERE CAMPO LIKE ' + #39 + Edit1.Text + #37 + #39 + ' ORDER BY CAMPO');
Query1.Active := True;

                If Query1.FieldByName('CAMPO').AsString <> '' then

                begin

                        Posicao := length(Edit1.Text);

                        For Aux := length(Edit1.Text)+1 to Length(Query1.FieldByName('Tratamento').AsString) do

                        begin

                                Edit1.Text := Edit1.Text + Query1.FieldByName('Tratamento').AsString[Aux];

                        end;

                        Edit1.SelStart := Posicao;

                        Edit1.SelLength := length(Edit1.Text);

                end;

        end;

        Except

end;

end;