Database: architecture
Question: What are the 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