Find the delegates who are from counties with population below 100000.
SELECT T2.Delegate FROM county AS T1 JOIN election AS T2 ON T1.County_id  =  T2.District WHERE T1.Population  <  100000
delegates from counties with population below 100000 refers to SELECT ... FROM ... JOIN ... ON ... WHERE Population < 100000; counties relate to county table; delegates relate to election table; population of county is a field in the county table; linking between delegates and their counties requires a JOIN between county and election tables on a common identifier.