CREATE TABLE allergy_type (allergy TEXT, allergytype TEXT)
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)

Give the advisor with the most students.
SELECT advisor FROM student GROUP BY advisor ORDER BY COUNT(*) DESC LIMIT 1
SELECT "advisor" FROM "student" GROUP BY "advisor" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1