Tell me all the names of the counties.
select county_name from county
Okay. I want to know their delegates.
select t2.delegate from county as t1 join election as t2 on t1.county_id = t2.district
Furthermore, please tell me which ones' population is larger than 50000?
select t2.delegate from county as t1 join election as t2 on t1.county_id = t2.district where t1.population > 50000
Wonderful! How many unique ones are there?
select count(distinct t2.delegate) from county as t1 join election as t2 on t1.county_id = t2.district where t1.population > 50000