U2 เล่นวันไหน?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
On what flight day was U2 played?It is not neccessary to use all the tables.
 table_name_2:  (flight_day [ VARCHAR ] artist [ VARCHAR) ]
SELECT flight_day FROM table_name_2 WHERE artist = "u2"