CREATE TABLE lesson_students (
lesson_id integer,
student_id integer,
visit boolean DEFAULT false
);
CREATE TABLE students (
id integer NOT NULL,
name character varying(10)
);
WITH t AS (
SELECT json_build_object('id', s.id,'name', s.name, 'visit', lesson_students.visit) d
FROM lesson_students
JOIN students s on lesson_students.student_id = s.id
WHERE lesson_students.lesson_id = 8
) SELECT JSON_AGG(d) FROM t;