how to create a composite primary key in postgresql code example

Example 1: postgres composite primary key

CREATE TABLE course_grades (
    quarter_id INTEGER,
    course_id TEXT,
    student_id INTEGER,
    grade INTEGER,
    PRIMARY KEY(quarter_id, course_id, student_id)
);

Example 2: postgres composite primary key

PRIMARY KEY(pk_1, pk_2, ..., pk_n)