Listbox add items from database and sort + delete duplicates

Question

I'd need some help since I don't see any solution after doing some search...

I have a database Database.mdb, which have a few tables, I'm reading specific table Fixtures, which have fields ID, ChNo, Default and Manufacturer;

I then have a form on which I'd like a user to be able to choose from each fixture, but would like to sort it by manufacturer firstly. So, I added ListBox component on a form, and started to populate it using the code provided:

    procedure TPatchNew1.FormShow(Sender: TObject);
var No, No2: integer;
begin
No2:=0;
AdoQuerySearchFixtures.SQL.Text:='SELECT Manufacturer FROM Fixtures';
AdoQuerySearchFixtures.Open;
ManuNo:=AdoQuerySearchFixtures.RecordCount;
While No2 < No do
  begin
  ManufacturerListbox.Items.Add;
  AdoQuerySearchFixtures.Close;
  AdoQuerySearchFixtures.SQL.Clear;
  AdoQuerySearchFixtures.SQL.Text:='SELECT Manufacturer FROM Fixtures WHERE ID='+IntToStr(No2+1);
  AdoQuerySearchFixtures.Open;
  ManufacturerListbox.Items[No2].Caption:=AdoQuerySearchFixtures.Fields[0].AsString;
  No2:=No2+1;
  end;

end;

This does the trick, but I'd like it to first: merge all duplicates, so that the fixtures with the same Manufacturer field value are all shown only after the Listbox item is clicked (I believe I'll be able to do that changing SQL text to "WHERE Manufacturer=something"), but there are not 100 items in listbox, if I have 90 fixtures from same manufacturer; At last, before the listbox is populated, I'd like it to be sorted alphabetically, from A to Z. Should I firstly read all manufacturers to sort of a record or array, then find duplicates and delete them, and later sort it, lastly filling in to listbox items, or is there any other way? It that's the way, how to do it? I give up after this whole day.. :(

Thanks.

Cheers

Answer 1

If I understand you correctly, you want to display in a listbox the names of manufacturers who supply fixtures. It's not clear from your question, but I am assuming that you have at least two tables: one of manufacturers and one of fixtures. The manufacturer will be a foreign key in the fixtures table.

If you want to load the listbox with the manufacturers, then it is better to take the data from the manufacturers table as you are (almost) guaranteed to have no duplicates there. Your sql query would be

select id, name 
from manufacturers
order by name

If you want only manufacturers who appear in the fixtures table, then alter the query thus

select id, name
from manufacturers
where exists (select 1 from fixtures
where fixtures.manufacturer = manufacturers.id)
order by name

Load the listbox in the following manner

manulist.items.clear;
with qManufacturers do
 begin
  open;
  while not eof do
   begin
    manulist.items.addobject (fieldbyname ('name').asstring,
                              tobject (fieldbyname ('id').asinteger));
    next
   end;
  close
 end;

Then when a name is chosen from the listbox, you can display the fixtures thus

with manulist do
 begin
  manu:= longint (Items.Objects[itemindex]);  // manufacturer key
  mname:= items[itemindex];                   // manufacturer name
 end;

with qFixtures do begin params[0].asinteger:= manu; open; .... end;

qFixtures would be something like

select id, name, ...
from fixtures
where manufacturer = :p1