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)

Show the student id of the oldest student.
SELECT stuid FROM student WHERE age = (SELECT MAX(age) FROM student)
SELECT "stuid" FROM "student" WHERE "age" = (SELECT MAX("age") FROM "student")