CREATE TABLE trainingSchedule (
    id NUMBER,
    training_date DATE
);

DECLARE
  start_date NUMBER;
  end_date NUMBER;
  training_date DATE;
  day_of_week NUMBER;
  training_id NUMBER := 1;
BEGIN

  start_date := TO_NUMBER(TO_CHAR(TO_DATE(sysdate, 'dd.MM.yy'), 'j'));
  end_date := TO_NUMBER(TO_CHAR(TO_DATE('31.12.2021', 'dd.MM.yy'), 'j'));
  
  FOR selected_date IN start_date..end_date LOOP
    training_date := TO_CHAR(TO_DATE(selected_date, 'j'), 'dd.MM.yy');
    SELECT TO_CHAR(training_date, 'D') INTO day_of_week FROM DUAL;
    IF (day_of_week IN (1, 3, 5)) THEN
        BEGIN
            INSERT INTO trainingSchedule VALUES(training_id, training_date);
            SELECT max(id) INTO training_id FROM trainingSchedule;
            training_id := training_id + 1;
        END;
    END IF;
  END LOOP;
END;