What are the ids, names and genders of the architects who built two bridges or one mill?
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