var
yourtxt: textfile;
recordstr: widestring;

yourtxt := assignfile("exportdb.txt");
rewrite(yourtxt);

dbgrid.datasource.dataset.first;
while not dbgrid.datasource.dataset.eof do
begin
recordstr := dbgrid.datasource.dataset.fieldbyname('field1').AsString+dbgrid.datasource.dataset.fieldbyname('field2').AsString+....;
writeln(yourtxt, recordstr);
dbgrid.datasource.dataset.next;
end;
closefile(yourtxt);