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

Which allergy type is most common?
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 FETCH FIRST 1 ROWS ONLY