PAL M รุ่นใดมี PAL I 50HZ?ไม่จำเป็นต้องใช้ตารางทั้งหมด
Which PAL M has a PAL I of 50HZ?It is not neccessary to use all the tables.
 table_name_55:  (pal_m [ VARCHAR ] pal_i [ VARCHAR) ]
SELECT pal_m FROM table_name_55 WHERE pal_i = "50hz"