Notes on the BITAND Function
The current implementation of BITAND defines n = 128.
PL/SQL supports an overload of BITAND for which the types of the inputs and of the result are all BINARY_INTEGER and for which n = 32.
结论：如果要在pl/sql里面对超过32位的数做bitand，不能用result:=bitand(a,b);而要用select bitand(a,b) into result from dual;