CREATE OR REPLACE FUNCTION get_doctor_appoint()
RETURNS TEXT AS $$
DECLARE 
Names TEXT DEfault '';
rec_appoint RECORD;
doctor_appoint cursor 
FOR SELECT * FROM appointments 
where doctorAMKA = (SELECT doctoramka FROM doctor WHERE username='foo@bar.net')
AND t>'2017-4-6 00:00:00' AND t<'2017-5-6 00:00:00';
BEGIN
OPEN doctor_appoint; 

LOOP
FETCH doctor_appoint INTO rec_appoint;
EXIT WHEN NOT FOUND;
Names:=Names||','||rec_appoint.t||':'||rec_appoint.patientamka;
END LOOP;
CLOSE doctor_appoint;
RETURN Names;
END; $$
LANGUAGE plpgsql;