วันไหนมีสเตจ ss11?ไม่จำเป็นต้องใช้ทุกตาราง
Which days have a stage of ss11?It is not neccessary to use all the tables.
 table_21536557_2:  (day [ VARCHAR ] stage [ VARCHAR) ]
SELECT day FROM table_21536557_2 WHERE stage = "SS11"