CREATE TABLE Student (
        StuID        INTEGER PRIMARY KEY,
        LName        VARCHAR(12),
        Fname        VARCHAR(12),
        Age      INTEGER,
        Sex      VARCHAR(1),
        Major        INTEGER,
        Advisor      INTEGER,
        city_code    VARCHAR(3)
 )

CREATE TABLE Dorm (
       dormid		INTEGER,
       dorm_name	VARCHAR(20),
       student_capacity	INTEGER,
       gender			VARCHAR(1)
)

CREATE TABLE Dorm_amenity (
       amenid			INTEGER,
       amenity_name		VARCHAR(25)
)

CREATE TABLE Has_amenity (
       dormid			INTEGER,
       amenid				INTEGER,
	FOREIGN KEY (dormid) REFERENCES `Dorm`(dormid),
	FOREIGN KEY (amenid) REFERENCES `Dorm_amenity`(amenid)
)

CREATE TABLE Lives_in (
       stuid 	      INTEGER,
       dormid		INTEGER,
       room_number	INTEGER,
	FOREIGN KEY (stuid) REFERENCES `Student`(StuID),
        FOREIGN KEY (dormid) REFERENCES `Dorm`(dormid)
)
SELECT lname FROM student WHERE sex  =  'F' AND city_code  =  'BAL' UNION SELECT lname FROM student WHERE sex  =  'M' AND age  <  20
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.