Делай параметризиарованный запрос:
Код:
SELECT * FROM ":bux:intt.db"
WHERE kat = :A AND data >= :B AND data <= :C
ORDER BY data
...
Query1.Active := False;
Query1.ParamByName('A').AsString := a;
Query1.ParamByName('B').AsDateTime := b;
Query1.ParamByName('C').AsDateTime := c;
Query1.Active := True;