CREATE TABLE student (stuid NUMBER, lname CLOB, fname CLOB, age NUMBER, sex CLOB, major NUMBER, advisor NUMBER, city_code CLOB)
CREATE TABLE has_amenity (dormid NUMBER, amenid NUMBER)
CREATE TABLE dorm (dormid NUMBER, dorm_name CLOB, student_capacity NUMBER, gender CLOB)
CREATE TABLE dorm_amenity (amenid NUMBER, amenity_name CLOB)
CREATE TABLE lives_in (stuid NUMBER, dormid NUMBER, room_number NUMBER)

Find the last name of students who is either female (sex is F) and living in the city of code BAL or male (sex is M) and in age of below 20.
SELECT lname FROM student WHERE sex = 'F' AND city_code = 'BAL' UNION SELECT lname FROM student WHERE sex = 'M' AND age < 20
SELECT "lname" FROM "student" WHERE "city_code" = 'BAL' AND "sex" = 'F' UNION SELECT "lname" FROM "student" WHERE "age" < 20 AND "sex" = 'M'