Database: architecture
Question: What are ids, names and genders of the architects who built two bridges or one mill?
SQL: select t1.id ,  t1.name ,  t1.gender from architect as t1 join bridge as t2 on t1.id  =  t2.architect_id group by t1.id having count(*)  =  2 union select t1.id ,  t1.name ,  t1.gender from architect as t1 join mill as t2 on t1.id  =  t2.architect_id group by t1.id having count(*)  =  1