CREATE TABLE Students (student_id NUMBER, student_details VARCHAR2)
CREATE TABLE Courses (course_id VARCHAR2, course_name VARCHAR2, course_description VARCHAR2, other_details VARCHAR2)
CREATE TABLE Candidates (candidate_id NUMBER, candidate_details VARCHAR2)
CREATE TABLE Student_Course_Attendance (student_id NUMBER, course_id NUMBER, date_of_attendance DATETIME)
CREATE TABLE Student_Course_Registrations (student_id NUMBER, course_id NUMBER, registration_date DATETIME)
CREATE TABLE Candidate_Assessments (candidate_id NUMBER, qualification CHAR, assessment_date DATETIME, asessment_outcome_code CHAR)
CREATE TABLE Addresses (address_id NUMBER, line_1 VARCHAR2, line_2 VARCHAR2, city VARCHAR2, zip_postcode CHAR, state_province_county VARCHAR2, country VARCHAR2)
CREATE TABLE People_Addresses (person_address_id NUMBER, person_id NUMBER, address_id NUMBER, date_from DATETIME, date_to DATETIME)
CREATE TABLE People (person_id NUMBER, first_name VARCHAR2, middle_name VARCHAR2, last_name VARCHAR2, cell_mobile_number VARCHAR2, email_address VARCHAR2, login_name VARCHAR2, password VARCHAR2)

For each course id, how many students are registered and what are the course names, sort by the Y in descending.
SELECT course_name, COUNT(*) FROM Students AS T1 JOIN Student_Course_Registrations AS T2 ON T1.student_id = T2.student_id JOIN Courses AS T3 ON T2.course_id = T3.course_id GROUP BY T2.course_id ORDER BY COUNT(*) DESC
SELECT "course_name", COUNT(*) FROM "Students" "T1" JOIN "Student_Course_Registrations" "T2" ON "T1"."student_id" = "T2"."student_id" JOIN "Courses" "T3" ON "T2"."course_id" = "T3"."course_id" GROUP BY "T2"."course_id" ORDER BY COUNT(*) DESC