[ContraVeneno]

Código Delphi [-]
with UnQuery do begin
 If active then close;
 SQL.Clear;
 SQL.Add('Select LosCampos ');
 SQL.Add('From UnTabla');
 Case ComboBox1.ItemIndex Of Begin
  0:   SQL.Add('Where Codigo = :Valor ');
  1:   SQL.Add('Where Nombre = :Valor ');
  2:   SQL.Add('Where Producto = :Valor ');
 end; //Case
 ParamByname('Valor').AsString := UnEdit.Text;
 Open;
end;  //with