DELETE FROM courses WHERE id_course = 'course170';
DELETE FROM courses WHERE id_course = 'course32';
DELETE FROM courses WHERE id_course = 'course157';
DELETE FROM courses WHERE id_course = 'course67';
DELETE FROM courses WHERE id_course = 'course51';
DELETE FROM courses WHERE id_course = 'course162';
DELETE FROM courses WHERE id_course = 'course30';
DELETE FROM courses WHERE id_course = 'course8';
DELETE FROM courses WHERE id_course = 'course103';
DELETE FROM courses WHERE id_course = 'course121';
