How many more black female victims than white female victims were discovered?
black refers to race = 'B'; female refers to gender = 'F'; white refers to race = 'W'; result = subtract(count(victims where race = 'B'), count(victims where race = 'W')) where gender = 'F'
SELECT SUM(race = 'B') - SUM(race = 'W') FROM subjects WHERE gender = 'F'