[2175#_MEDIUM] The Change in Global Rankings

[2159#_MEDIUM] Order Two Columns Independently

[1479#_HARD] Sales by Day of the Week

[1412#_HARD] Find the Quiet Students in All Exams

[2142#_MEDIUM] The Number of Passengers in Each Bus I

[2112#_MEDIUM] The Airport With the Most Traffic

[2084#_MEDIUM] Drop Type 1 Orders for Customers With Type 0 Orders -- 문제를 잘 읽자

[1384#_HARD] Total Sales Amount by Year -- 이거 못 품