Delphi: Reading number of columns + names from dataset?

Question

Hello

Since Embarcadero's NNTP server stopped responding since yesterday, I figured I could ask here: I work with a non-DB-aware grid, and I need to loop through a dataset to extract the number of columns, their name, the number of rows and the value of each fields in each row.

I know to read the values for all the fields in each row, but I don't know how to extract column-related information. Does someone have some code handy?

procedure TForm1.FormCreate(Sender: TObject);
var
  index : Integer;
begin
  With ASQLite3DB1 do begin
      DefaultDir := ExtractFileDir(Application.ExeName);
      Database := 'test.sqlite';
      CharacterEncoding := 'STANDARD';
      Open;
  end;

  With ASQLite3Query1 do begin
    ASQLite3Query1.Connection := ASQLite3DB1;

    SQL.Text := 'CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, label VARCHAR)';
    ExecSQL;

    SQL.Text := 'INSERT INTO mytable (label) VALUES ("dummy label")';
    ExecSQL;

    SQL.Text := 'SELECT id AS Identification, label AS Label FROM mytable';
    Open;

    //How to get column numbers + names to initialized grid object?
    for index := 0 to ASQLite3Query1. - 1 do begin

    end;

    for index := 0 to FieldCount - 1 do begin
      ShowMessage(Fields[index].AsString);
    end;
  end;
end;

Thank you.

Answer 1

Number of fields and their names could be acquired as follows:

procedure TForm1.Button1Click(Sender: TObject);
begin
  with Query1 do
  begin
 ShowMessage(IntToStr(FieldCount));
 ShowMessage(Fields[0].FieldName);
  end;
end;

You can checkout TFieldDef for more detail info about the field.

dataset.FieldDefs[0] has properties like DataType and Size.

Answer 2

If what you're looking for is a list of field names, try creating a TStringList and passing it to the TDataset.Fields.GetFieldNames procedure.

If you want more information about fields, the TFields object (ASQLite3Query1.Fields) has a default property and a Count property, so you can use it like an array, and an enumerator, both of which can be used to loop over each TField object and retrieve its metadata.