Table schema:
CREATE TABLE student_course_registrations (student_id VARCHAR, course_id VARCHAR, registration_date VARCHAR); CREATE TABLE courses (course_id VARCHAR, course_name VARCHAR)

Question: List the id of students who registered course statistics in the order of registration date.
SQL: SELECT T2.student_id FROM courses AS T1 JOIN student_course_registrations AS T2 ON T1.course_id = T2.course_id WHERE T1.course_name = "statistics" ORDER BY T2.registration_date