SELECT T2.friend FROM Person AS T1 JOIN PersonFriend AS T2 ON T1.name  =  T2.name WHERE T1.name  =  'Bob'
Who are the friends of Bob?
CREATE TABLE Person (
  name varchar(20) PRIMARY KEY,
  age INTEGER,
  city TEXT,
  gender TEXT,
  job TEXT
);

CREATE TABLE PersonFriend (
  name varchar(20),
  friend varchar(20),
  year INTEGER,
  FOREIGN KEY (name) REFERENCES Person(name),
  FOREIGN KEY (friend) REFERENCES Person(name)
);

INSERT INTO Person VALUES ('Alice',25,'new york city','female','student');
INSERT INTO Person VALUES ('Bob',35,'salt lake city','male','engineer');
INSERT INTO Person VALUES ('Zach', 45,'austin','male','doctor');
 INSERT INTO Person VALUES ('Dan',26,'chicago','female','student');

INSERT INTO PersonFriend VALUES ('Alice','Bob',10);
INSERT INTO PersonFriend VALUES ('Zach','Dan', 12);
INSERT INTO PersonFriend VALUES ('Bob','Zach', 5);
INSERT INTO PersonFriend VALUES ('Zach','Alice', 6);
