CREATE TABLE table_name_20 (tujia_population NUMBER, prefecture VARCHAR2, county VARCHAR2)

What is the sum of Tujia population with the Zhangjiajie prefecture in Sangzhi county?
SELECT SUM(tujia_population) FROM table_name_20 WHERE prefecture = "zhangjiajie" AND county = "sangzhi"
SELECT SUM("tujia_population") FROM "table_name_20" WHERE "county" = "sangzhi" AND "prefecture" = "zhangjiajie"