SELECT *
FROM students
WHERE student_id NOT IN
  ( SELECT DISTINCT s.student_id
    FROM students s
      JOIN coursestudent cs ON s.student_id = cs.student_id
      JOIN marks m ON cs.id = m.coursestudent_id
    WHERE m.mark < 60)

DELETE FROM students WHERE student_id ANY (SELECT student_id FROM students WHERE student_id NOT IN (SELECT DISTINCT s.student_id FROM students s JOIN coursestudent cs ON s.student_id = cs.student_id JOIN marks m ON cs.id = m.coursestudent_id WHERE m.mark < 60));

CREATE TABLE `students` (
  `student_id` int(11) NOT NULL auto_increment,
  `student_name` varchar(50) NOT NULL,
  `group_id` int(11) NOT NULL,
  PRIMARY KEY  (`student_id`),
  KEY `student_group_fk` (`group_id`),
  CONSTRAINT `student_group_fk` FOREIGN KEY (`group_id`) REFERENCES `groups` (`group_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE `coursestudent` (
  `id` int(11) NOT NULL auto_increment,
  `student_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  PRIMARY KEY  (`id`),
  KEY `coursestudentlecturer_student_fk` (`student_id`),
  KEY ` coursestudentlecturer_course_fk` (`course_id`),
  CONSTRAINT ` coursestudentlecturer_course_fk` FOREIGN KEY (`course_id`) REFERENCES `courses` (`course_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `coursestudentlecturer_student_fk` FOREIGN KEY (`student_id`) REFERENCES `students` (`student_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE `marks` (
  `coursestudent_id` int(11) NOT NULL,
  `mark` decimal(5,2) NOT NULL,
  `lecturer_id` int(11) NOT NULL,
  KEY `marks_coursestudent_fk` (`coursestudent_id`),
  KEY ` marks_lecturer_fk` (`lecturer_id`),
  CONSTRAINT ` marks_lecturer_fk` FOREIGN KEY (`lecturer_id`) REFERENCES `lecturers` (`lecturer_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `marks_coursestudent_fk` FOREIGN KEY (`coursestudent_id`) REFERENCES `coursestudent` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

DELETE FROM students WHERE student_id IN (SELECT * FROM (SELECT student_id FROM students WHERE student_id NOT IN (SELECT DISTINCT s.student_id FROM students s JOIN coursestudent cs ON s.student_id = cs.student_id JOIN marks m ON cs.id = m.coursestudent_id WHERE m.mark < 60)) AS t);