CREATE TABLE Subjects (subject_id NUMBER, subject_name VARCHAR2)
CREATE TABLE Student_Course_Enrolment (registration_id NUMBER, student_id NUMBER, course_id NUMBER, date_of_enrolment DATETIME, date_of_completion DATETIME)
CREATE TABLE Course_Authors_and_Tutors (author_id NUMBER, author_tutor_ATB VARCHAR2, login_name VARCHAR2, password VARCHAR2, personal_name VARCHAR2, middle_name VARCHAR2, family_name VARCHAR2, gender_mf VARCHAR2, address_line_1 VARCHAR2)
CREATE TABLE Students (student_id NUMBER, date_of_registration DATETIME, date_of_latest_logon DATETIME, login_name VARCHAR2, password VARCHAR2, personal_name VARCHAR2, middle_name VARCHAR2, family_name VARCHAR2)
CREATE TABLE Student_Tests_Taken (registration_id NUMBER, date_test_taken DATETIME, test_result VARCHAR2)
CREATE TABLE Courses (course_id NUMBER, author_id NUMBER, subject_id NUMBER, course_name VARCHAR2, course_description VARCHAR2)

Visualize the general trend of the number of date of completion over the date of completion, and rank by the X-axis in desc.
SELECT date_of_completion, COUNT(date_of_completion) FROM Student_Course_Enrolment GROUP BY date_of_completion ORDER BY date_of_completion DESC
SELECT "date_of_completion", COUNT("date_of_completion") FROM "Student_Course_Enrolment" GROUP BY "date_of_completion" ORDER BY "date_of_completion" DESC