Z gory dzieki za podpowiedzi.
SELECT DATA,SUM( WPLATY) AS sum_wplaty FROM UTARG WHERE DATA BETWEEN '2010-01-05' AND '2010-01-15' GROUP BY DATA
Zapytanie zwraca
DATA sum_wynik
2010-01-05 122.6
2010-01-06 164.2
2010-01-07 23.3
2010-01-08 10.4
2010-01-09 19.65
2010-01-10 43.4
2010-01-11 9.2
2010-01-12 6.2
2010-01-13 125.75