text: 
  
  drop table users if exists;
  drop table friend if exists;
  
  create table users (
    id int,
    name varchar(20)
  );
  
  create table friend (
    user_id int,
    friend_id int
  );
  
  insert into users (id, name) values
  (1, 'User1'), (2, 'User2'), (3, 'User3');
  
  insert into friend (user_id, friend_id) values
  (1, 2), (2, 2), (2, 3);
  
  drop table blog if exists;
  drop table author if exists;
  
  create table blog (
    id int,
    title varchar(16),
    author_id int,
    co_author_id int
  );
  
  create table author (
    id int,
    name varchar(16),
    reputation int
  );
  
  insert into blog (id, title, author_id, co_author_id) values
  (1, 'Blog1', 1, 2), (2, 'Blog2', 2, 3);
  
  insert into author (id, name, reputation) values
  (1, 'Author1', 1), (2, 'Author2', 2), (3, 'Author3', 3);
  