[Grunch]

Код:

SELECT data,kat,summ
FROM ":bux:intt.db"
WHERE (kat = a)
        AND (data>=DateToStr(b))
        AND (data<=DateToStr(c))

или

Код:

SELECT data,kat,summ
FROM ":bux:intt.db"
WHERE (kat = a)
        AND (data between DateToStr(b) and DateToStr(c))