text: select StudentId, StudentName, GroupId
  from Students
  where exists (
      select Mark
      from Marks
      where Mark = :Mark
        and Marks.StudentId = Students.StudentId
        and exists (
          select CourseId
          from Courses
          where CourseName = :CourseName
            and Courses.CourseId = Marks.CourseId
        )
    )
  