CREATE TABLE Students (
first_name VARCHAR(20),
last_name VARCHAR(20),
birthday DATE,
s_id INT, 
CONSTRAINT pk_Students PRIMARY KEY (s_id)
);

CREATE TABLE Enrolments (
s_id INT, 
course_code VARCHAR(20),
year INT, 
CONSTRAINT fk_Enrolments FOREIGN KEY (s_id)
REFERENCES Students(s_id)
);