DROP TABLE IF EXISTS subject;
CREATE TABLE IF NOT EXISTS subject (                  # Comment
    subject_id  INT UNSIGNED NOT NULL AUTO_INCREMENT, # Subject ID
    subject     VARCHAR(25)  NOT NULL,                # Subject name
    parent_id   INT UNSIGNED     NULL DEFAULT NULL,   # Parent ID as seen from
    PRIMARY KEY (subject_id),                         # the diagram refers to
    UNIQUE (subject),                                 # the subject_id field
    INDEX (parent_id),
    CONSTRAINT fk_subject_parent
    FOREIGN KEY (parent_id)
        REFERENCES subject (subject_id)
            ON DELETE RESTRICT
            ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO subject (subject, parent_id) VALUES
                    ('Science',    NULL),
                    ('Mathematics',   1),
                    ('Calculus',      2),
                    ('Algebra',       2),
                    ('Geometry',      2),
                    ('Languages',  NULL),
                    ('English',       6),
                    ('Latin',         6);

SELECT * FROM subject;
╔════════════╦═════════════╦═══════════╗
║ subject_id ║   subject   ║ parent_id ║
╠════════════╬═════════════╬═══════════╣
║          1 ║ Science     ║      NULL ║
║          2 ║ Mathematics ║         1 ║
║          3 ║ Calculus    ║         2 ║
║          4 ║ Algebra     ║         2 ║
║          5 ║ Geometry    ║         2 ║
║          6 ║ Languages   ║      NULL ║
║          7 ║ English     ║         6 ║
║          8 ║ Latin       ║         6 ║
╚════════════╩═════════════╩═══════════╝

DELIMITER$$

DROP PROCEDURE IF EXISTS get_parent_subject_list;
CREATE PROCEDURE get_parent_subject_list ()
BEGIN
    SELECT subject_id, subject
    FROM subject
    WHERE parent_id IS NULL
    ORDER BY subject ASC;
END$$


DROP PROCEDURE IF EXISTS get_child_subject_list;
CREATE PROCEDURE get_child_subject_list (IN parentID INT)
BEGIN
    SELECT subject_id, subject
    FROM subject
    WHERE parent_id = parentID
    ORDER BY subject ASC;
END$$

DELIMITER ;

procedure TForm1.CreateSubjectTreeView(Sender: TObject);
var
    i : integer;
begin
    i := 0;

    q1.SQL.Clear;
    q1.SQL.Add('CALL get_parent_subject_list()');
    q1.Open;
    q1.First;

    while not q1.EOF do
    begin
        TreeView.Items.Add(nil, q1.Fields[1].Value);

        q2.SQL.Clear;
        q2.SQL.Add('CALL get_child_subject_list(' +
                    VarToStr(q1.Fields[0].Value) + ')');
        q2.Open;
        q2.First;

        while not q2.EOF do
        begin
            TreeView.Items.AddChild(TreeView.Items.Item[i], q2.Fields[1].Value);
            q2.Next;
        end;

        i := TreeView.Items.Count;
        q1.Next;
    end;
end;

+- Science
|   |
|   +- Mathematics
|
+- Languages
    |
    +- English
    +- Latin

+- Science
|   |
|   +- Mathematics
|       |
|       +- Calculus
|       +- Algebra
|       +- Geometry
|
+- Languages
    |
    +- English
    +- Latin

Select ID, Title, This, That from TREE where Parent_ID = :ID

var i,imax,ikey,iParent : integer;
        aNode,aParentNode : TTreeNode;
        aData : TMyData;
        aContainer : TSparseObjectArray; // cDataStructs , delphi fundamentals
        aNodeIndex : TSparseObjectArray; // delphi 7
    begin
      try
        aContainer := TSparseObjectArray.Create(true);
        aNodeIndex := TSparseObjectArray.Create(False);
        imax := 10000;
        // create test data;
        for i := 1 to imax do
        begin
          aData := TMyData.Create;
          aData.iKey := i;
          aData.iParent := Random(imax); // random parent
          aData.Data := 'I:' + IntToStr(aData.iKey);
          aContainer.Item[i] := aData;
        end;

        tv1.Items.Clear;
        tv1.Items.BeginUpdate;
        // build tree
        // First Pass - build root tree nodes and create cross ref. index
        for i := 1 to imax do
        begin
          aData := TMYData(aContainer.Item[i]);
          aNode := tv1.Items.AddChild(nil,aData.Data);
          aNodeIndex.Item[aData.iKey] := aNode;
        end;
        // Second Pass - find parent node using index and move node
        for i := 1 to imax do
        begin
          aData := TMYData(aContainer.Item[i]);
          aNode := TTreeNode(aNodeIndex.Item[aData.iKey]);
          if aNodeIndex.HasItem(aData.iparent)
          then begin
                 aParentNode := TTreeNode(aNodeIndex.Item[aData.iparent]);
                 aNode.MoveTo(aParentNode,naAddChild);
               end;
        end;
        tv1.Items.EndUpdate;
        tv1.Select( tv1.Items.GetFirstNode);
      finally
        aContainer.Free;
        aNodeIndex.free;
      end;
  end;

type
    tElementoMenu = Class(TObject)
      Comando : String;
      //Nombre : String;
      ID : String;
    End;
...
procedure TForm1.CrearMenuDeArbol(dsOrigen: TDataSource; CampoID, IDPadre,
  CampoComando, CampoCaption, CampoVisible: String; Raiz : TTreeNode = Nil);
var
  RamaActual, PrimeraRama : TTreeNode;
  ElementoMenu : TElementoMenu;
  iIndiceImagen : Integer;
begin
  RamaActual := Nil;
  PrimeraRama := Nil;
  if not assigned(Raiz) then
    VaciarArbol;

  with dsOrigen.DataSet do
  begin
    //For this example I use filter, however it can be use with WHERE sentence
    Filtered := False;
    IF not assigned(Raiz) then
      Filter := IdPadre + ' IS NULL '
    else
      Filter := IDPadre + ' = ' + TElementoMenu(Raiz.Data).ID;
    Filtered := True;

    First;
    while not Eof do
    begin
      if FieldByName(CampoVisible).AsString = 'Y' then
      begin
        ElementoMenu := TElementoMenu.Create;
        ElementoMenu.Comando := FieldByName(CampoComando).AsString;
        ElementoMenu.ID := FieldByName(CampoID).AsString;
        //ElementoMenu.Nombre := FieldByName(CampoName).AsString; //Otros datos para agregar al elemento del menu
        iIndiceImagen := 0;
        if Not Assigned(Raiz) then
          RamaActual := TreeView1.Items.AddObject(Nil, FieldByName(CampoCaption).AsString, ElementoMenu )
        else
        Begin
          RamaActual := TreeView1.Items.AddChildObject(Raiz, FieldByName(CampoCaption).AsString, ElementoMenu );
          iIndiceImagen := 1;
        End;

        RamaActual.ImageIndex := iIndiceImagen;
        RamaActual.SelectedIndex := iIndiceImagen;
      end;
      Next;
    end;

    if not Assigned(Raiz) then
      PrimeraRama := TreeView1.Items.GetFirstNode
    else
      PrimeraRama := Raiz.getFirstChild;

    while Assigned(PrimeraRama) do
    begin
      CrearMenuDeArbol(dsOrigen, CampoID, IDPadre, CampoComando, CampoCaption, CampoVisible, PrimeraRama);
      PrimeraRama := PrimeraRama.getNextSibling;
    end;
  end;
end;


procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  VaciarArbol;
end;

procedure TForm1.TreeView1DblClick(Sender: TObject);
begin
  if Assigned(treeView1.Selected) then
    ShowMessage(TElementoMenu(treeView1.Selected.Data).Comando);
end;

procedure TForm1.VaciarArbol;
var
  itm : TTreeNode;
begin
  while TreeView1.Items.Count > 0 do
  begin
    itm := TreeView1.Items[TreeView1.Items.Count-1];
    TElementoMenu(itm.Data).Free;
    TreeView1.Items.Delete(itm);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  CrearMenuDeArbol(ds1, 'ID', 'PID', 'NAME', 'CAPTION', 'ISVISIBLE');
  Treeview1.FullExpand;
end;