@DeleteMapping("/delete/student/{studentId}")

@Transactional
public void deleteStudent(String studentId) { ... }

@Transactional
public void deleteStudent(String studentId) {
    // 1단계: deleteByStudentId()에서 이미 DELETE 쿼리 실행
    Student deletedStudent = studentRepository.deleteByStudentId(studentId);
    
    // 2단계: 이미 삭제된 엔티티를 다시 삭제 시도 (불필요하고 위험!)
    studentRepository.delete(deletedStudent);
}

@Transactional
public void deleteStudent(String studentId) {
    // 1단계: 엔티티 존재 여부 확인
    Student student = studentRepository.findByStudentId(studentId)
        .orElseThrow(() -> new IllegalArgumentException("존재하지 않는 학생입니다."));
    
    // 2단계: 조회된 엔티티 삭제
    studentRepository.delete(student);
}

@DeleteMapping("/delete/student/{studentId}")
public void deleteStudent(@PathVariable String studentId) {
    studentService.deleteStudent(studentId);
    // 기본적으로 200 OK 반환
}

@DeleteMapping("/delete/student/{studentId}")
public ResponseEntity<Void> deleteStudent(@PathVariable String studentId) {
    studentService.deleteStudent(studentId);
    return ResponseEntity.noContent().build(); // 204 No Content
}