Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE Students (student_id VARCHAR); CREATE TABLE Student_Course_Enrolment (student_id VARCHAR)
### Question:
How many students did not have any course enrollment?
### Answer:
SELECT COUNT(*) FROM Students WHERE NOT student_id IN (SELECT student_id FROM Student_Course_Enrolment)