Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE student_course_registrations ( student_id VARCHAR )

### Question ###
what is id of students who registered some courses but the least number of courses in these students?

### Accurate SQL ###

SELECT student_id FROM student_course_registrations GROUP BY student_id ORDER BY COUNT(*) LIMIT 1