Show the countries that have both perpetrators with injures more than 50 and perpetrators with injures smaller than 20.
SELECT Country FROM perpetrator WHERE Injured  >  50 INTERSECT SELECT Country FROM perpetrator WHERE Injured  <  20
countries that have both = use INTERSECT; perpetrators with injures more than 50 refers to WHERE Injured > 50; perpetrators with injures smaller than 20 refers to WHERE Injured < 20;