It depends on the brand of amylase. Crosby and Baker is pure alpha, and won't give you much fermentables. ECKraus "Diatase" [sic] has both, and seems to work well enough on rice. Just don't use it on quinoa, oats, amaranth, or anything with lots of grain dust. The elevated proteins and beta-glucans in these grains, as well as the raw cellulose in the grain dust, will make it difficult to get a clear fermentable wort with just amylase.