CREATE TABLE PersonFriend (friend VARCHAR, name VARCHAR)
CREATE TABLE Person (name VARCHAR, gender VARCHAR)

Find the female friends of Alice.
SELECT T2.friend FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name = T2.friend WHERE T2.name = 'Alice' AND T1.gender = 'female'
SELECT "T2"."friend" FROM "Person" AS "T1" JOIN "PersonFriend" AS "T2" ON "T1"."name" = "T2"."friend" AND "T2"."name" = 'Alice' WHERE "T1"."gender" = 'female'