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 People_Addresses (person_address_id NUMBER, person_id NUMBER, address_id NUMBER, date_from DATETIME, date_to DATETIME)
CREATE TABLE Candidate_Assessments (candidate_id NUMBER, qualification CHAR, assessment_date DATETIME, asessment_outcome_code CHAR)
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)
CREATE TABLE Courses (course_id VARCHAR2, course_name VARCHAR2, course_description VARCHAR2, other_details VARCHAR2)
CREATE TABLE Students (student_id NUMBER, student_details VARCHAR2)
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 Candidates (candidate_id NUMBER, candidate_details VARCHAR2)

List the id of students who registered some courses and the number of their registered courses in a scatter chart
SELECT T1.student_id, COUNT(*) FROM Students AS T1 JOIN Student_Course_Registrations AS T2 ON T1.student_id = T2.student_id GROUP BY T1.student_id
SELECT "T1"."student_id", COUNT(*) FROM "Students" "T1" JOIN "Student_Course_Registrations" "T2" ON "T1"."student_id" = "T2"."student_id" GROUP BY "T1"."student_id"