CREATE TABLE student (stuid DECIMAL, lname TEXT, fname TEXT, age DECIMAL, sex TEXT, major DECIMAL, advisor DECIMAL, city_code TEXT)
CREATE TABLE has_allergy (stuid DECIMAL, allergy TEXT)
CREATE TABLE allergy_type (allergy TEXT, allergytype TEXT)

What is the largest major?
SELECT major FROM student GROUP BY major ORDER BY COUNT(*) DESC LIMIT 1
SELECT "major" FROM "student" GROUP BY "major" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1