Table: health_ethiopia
Columns: region
physician_gp_specialist
physician_population_ratio
health_officer
ho_population_ratio
all_nurses
nurse_population_ratio
mid_wives
mid_wife_population_ratio
hew

Question: What is the number of nurses in the region with an HO : Population Ratio of 1:16,791?
SQL: SELECT AVG("all_nurses") FROM health_ethiopia WHERE "ho_population_ratio" = '1:16,791'

Question: What is the number of physicians in the region with an all nurses number of 91?
SQL: SELECT MIN("physician_gp_specialist") FROM health_ethiopia WHERE "all_nurses" = 91