question: what is the highest % hydropower when % coal is 4.9 and % nuclear power is more than 0?
answer: SELECT MAX(_percentage_hydropower) FROM table_name_59 WHERE _percentage_coal = 4.9 AND _percentage_nuclear_power > 0
context: CREATE TABLE table_name_59 (_percentage_hydropower INTEGER, _percentage_coal VARCHAR, _percentage_nuclear_power VARCHAR)