CREATE TABLE Student (StuID NUMBER, LName VARCHAR2, Fname VARCHAR2, Age NUMBER, Sex VARCHAR2, Major NUMBER, Advisor NUMBER, city_code VARCHAR2)
CREATE TABLE Has_Allergy (StuID NUMBER, Allergy VARCHAR2)
CREATE TABLE Allergy_Type (Allergy VARCHAR2, AllergyType VARCHAR2)

Plot the total number by grouped by city code as a bar graph, could you list by the Y-axis in descending?
SELECT city_code, COUNT(*) FROM Student GROUP BY city_code ORDER BY COUNT(*) DESC
SELECT "city_code", COUNT(*) FROM "Student" GROUP BY "city_code" ORDER BY COUNT(*) DESC