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Caruso
Asked: 2020-07-07 15:06:43 +0800 CST 2020-07-07 15:06:43 +0800 CST

How to show 3 dependent DBGrid

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I have a program in Delphi and in the database I have a table of statistics categories (it has idand nombre), with the idea of ​​assigning each record productoa idcategory to group them.

I want to develop a form where when selecting a category of statistics from a grid or combo it shows me, in another grid, the products in that list (that is, those that have the one idin that list in the table productos) and, finally, another grid with those that are not associated, to be able to associate them.

I have a TClientDataSetand a TDataSetProvidernext to a TDataSourcefor the stat category table.

Then I did 1 TSQLQuerywith a parameter 'id':

 SELECT * FROM productos WHERE Categoria_E=':id';

And this other one:

 SELECT * FROM productos WHERE Categoria_E<>':id';

to associate them to the grids; also via a TClientDataSety provider .

It's okay like that?

If yes, in which event can I associate the value of the parameter idto refresh the grid?

delphi

1 Answers

  1. Best Answer

    It is not necessary to use the quotes inside the SQL when you use a parameter, because for the connection layer, this is already a text string, to declare the type of the parameter as string, so your SQL should look more like this:

    SELECT * FROM productos WHERE Categoria_E = :id;

    Then assuming you have the following TClientDataSetdeclared:

    • cdsCategoria( select * from Categoria)
    • cdsProductoEnCategoria( SELECT * FROM productos WHERE Categoria_E = :id)
    • cdsProductosNoCategoria( SELECT * FROM productos WHERE coalesce(Categoria_E, '') = :id)

    You can declare a method RefrescarProductos, like so:

    procedure TMiFormulario.RefrescarProductos;
  procedure RefrescarCDS(cds: TClientDataSet);
  begin
    if cds.Active then cds.Close;
    cds.Params.ParamByName('id').AsString := cdsCategoriaidCategoria.AsString;
    cds.Open;
  end;
begin
  RefrescarCDS(cdsProductosEnCategoria);
  RefrescarCDS(cdsProductosNoCategoria);
end;

    And finally call this method in the OnAfterOpenon events OnAfterScrollof the cdsCategoria, something like:

    procedure TMiFormulario.cdsCategoriaAfterOpen(Sender: TObject);
begin
  RefrescarProductos;
end;
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