ช่วยดูคำสั่ง sql ให้ด้วยครับ ความรู้น้อยถามบ่อยไม่ว่ากันนะครับ

SELECT samak_all.id_student
FROM samak_all LEFT JOIN register_all ON samak_all.id_student=register_all.id_student
WHERE register_all.id_student IS NULL


 OR (samak_all.id_student =(SELECT id_student FROM samak_all GROUP BY id_student HAVING COUNT(id_student)>1)



AND (

(SELECT COUNT(*) FROM samak_all 
 WHERE samak_all.id_student =(SELECT id_student FROM samak_all GROUP BY id_student HAVING COUNT(id_student)>1))

<>

(SELECT COUNT(*) FROM register_all 
 WHERE register_all.id_student =(SELECT id_student FROM samak_all GROUP BY id_student HAVING COUNT(id_student)>1))

) 

)
GROUP BY samak_all.id_student;