Ho una query tipo questa:
codice:
$query = "
	SELECT * FROM table
	WHERE campo = qualcosa
	GROUP BY data, periodo, valuta
	ORDER BY id DESC
";
Che restituisce una tabella tipo questa
Codice PHP:
while($row=mysql_fetch_array($result))
{
echo "<tr><td>$data</td><td>$periodo</td><td>$valuta</td><td>$valore</td></tr>";

2/23/2011    Morning    GBP    863.636
2/23/2011    Morning    EURO    1021.47
2/23/2011    Morning    USD    1401.25
2/22/2011    Evening    GBP    866.31
2/22/2011    Evening    EURO    1023.37
2/22/2011    Evening    USD    1401
2/22/2011    Morning    GBP    862.453
2/22/2011    Morning    EURO    1024.84
2/22/2011    Morning    USD    1394.5
2/21/2011    Evening    GBP    864.715
2/21/2011    Evening    EURO    1026.56
2/21/2011    Evening    USD    1403
2/21/2011    Morning    GBP    862.824
2/21/2011    Morning    EURO    1023.62
2/21/2011    Morning    USD    1399.5 
Ecco mi piacerebbe impaginarli in questo modo (non sto a variare i numeri... della tabella... ):

codice:
DATA      |          Morning            |           Evening
          | USD       EUR       GBP     | USD        EUR        GBP
2/23/2011 | 1401.25   1021.47   863.636 | 1401.25    1021.47    863.636
2/22/2011 | 1401.25   1021.47   863.636 | 1401.25    1021.47    863.636
2/21/2011 | 1401.25   1021.47   862.453 | 1401.25    1021.47    863.636
... ...   |