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

Which allergy type has most number of allergies?
SELECT allergytype FROM allergy_type GROUP BY allergytype ORDER BY COUNT(*) DESC LIMIT 1
SELECT "allergytype" FROM "allergy_type" GROUP BY "allergytype" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1