require 'mysql2'             # під'єднання бібліотеки mysql2
c = Mysql2::Client.new(      # створення сполучення
    :host     => '127.0.0.1',# адреса локального сервера (localhost)
    :username => 'root',     # обліковий запис користувача базами даних
    :password => '',         # пароль до облікового запису користувача БД
    :database => "school",   # назва бази даних
    :port     => 3306)       # порт сполучення

def all(r)
  r.each do |l|
    puts l
  end
  puts
end

a=["SELECT * FROM pupils WHERE form = '11Б';",
   "SELECT * FROM classroom WHERE (16 < capacity) and (capacity < 24);",
   "SELECT * FROM classroom WHERE capacity BETWEEN 17 AND 23;",
   "SELECT sename, name FROM pupils WHERE sename LIKE '%УК';",
   "SELECT sename, name FROM pupils WHERE name IN ( 'АНДРІЙ', 'ГРИГОРІЙ');",
   "SELECT COUNT(*) FROM pupils;",
   "SELECT quality, COUNT(no) FROM teachers GROUP BY quality;",
   "SELECT quality, COUNT(no) FROM teachers GROUP BY quality HAVING COUNT(no) > 1;",
   "SELECT sename,mark FROM marks WHERE (day='2020-09-24') ORDER BY mark;",
   "SELECT sename,mark FROM marks WHERE (day='2020-09-24') ORDER BY mark DESC;",
   "SELECT sename AS 'Прізвище',mark AS 'Оцінка' FROM marks WHERE (day='2020-09-24') ORDER BY mark DESC LIMIT 3,3;",
   "SELECT * FROM courses JOIN department ON courses.dept_name = department.dept_name;",
   "SELECT * FROM courses LEFT OUTER JOIN department ON courses.dept_name = department.dept_name;",
   "SELECT * FROM courses RIGHT OUTER JOIN department ON courses.dept_name = department.dept_name;"]
a.each do |b|
  puts b
  all(c.query(b))
end
c.close()