CREATE TABLE student (stuid NUMBER, lname CLOB, fname CLOB, age NUMBER, sex CLOB, major NUMBER, advisor NUMBER, city_code CLOB)
CREATE TABLE voting_record (stuid NUMBER, registration_date CLOB, election_cycle CLOB, president_vote NUMBER, vice_president_vote NUMBER, secretary_vote NUMBER, treasurer_vote NUMBER, class_president_vote NUMBER, class_senator_vote NUMBER)

Return the code of the city that has the most students.
SELECT city_code FROM student GROUP BY city_code ORDER BY COUNT(*) DESC LIMIT 1
SELECT "city_code" FROM "student" GROUP BY "city_code" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY