DELPHI - How work with memory table (TFDMemTable)

Variant 1) Copy data from TDataSet to TFDMemTable:

var
  pMemTable : TFDMemTable;
  pQuery : TFDQuery;
begin
  ...
  pMemTable := TFDMemTable.Create( self );
  pMemTable.CloneCursor( pQuery );
  ...

Variant 2) Define own structure of TFDMemTable:

var
  pMemTable : TFDMemTable;
  pQuery : TFDQuery;
begin
  ...
  pMemTable := TFDMemTable.Create( self );
  pMemTable.FieldDefs.Add( 'key', ftString, 25 );
  pMemTable.FieldDefs.Add( 'value', ftString, 25 );
  pMemTable.CreateDataSet();
  ...
  pMemTable.AppendRecord( [ 'firstkey', 'firstvalue' ] );
  ...