Table: tujia_population_2
Columns: province
prefecture
county
tujia_population
of_china_s_tujia_population

Question: Which province has a prefecture of Xiangxi with 0.81% of China's Tujia population?
SQL: SELECT "province" FROM tujia_population_2 WHERE "prefecture" = 'xiangxi' AND "of_china_s_tujia_population" = '0.81%'

Question: Which prefecture is in Hubei province and Enshi county?
SQL: SELECT "prefecture" FROM tujia_population_2 WHERE "province" = 'hubei' AND "county" = 'enshi'

Question: What is the sum of Tujia population with the Zhangjiajie prefecture in Sangzhi county?
SQL: SELECT SUM("tujia_population") FROM tujia_population_2 WHERE "prefecture" = 'zhangjiajie' AND "county" = 'sangzhi'