DROP TABLE POINTS;

CREATE TABLE POINTS (
    ID NUMBER,
    X  NUMBER,
    Y  NUMBER
);

CREATE OR REPLACE PROCEDURE GEN_POINT
IS
    X      NUMBER;
    Y      NUMBER;
    AMOUNT NUMBER;
BEGIN
    SELECT COUNT(*) INTO AMOUNT FROM POINTS;
    IF AMOUNT > 30 THEN
        EXECUTE IMMEDIATE 'TRUNCATE TABLE POINTS';
        AMOUNT := 0;
    ELSIF AMOUNT = 0 THEN
        X := 0;
        Y := 0;
    ELSE
        X := dbms_random.VALUE(1, 100);
        Y := dbms_random.VALUE(1, 100);
    END IF;
    INSERT INTO POINTS(ID, X, Y) VALUES (AMOUNT, X, Y);
END;
/

BEGIN
    DBMS_SCHEDULER.CREATE_JOB (
        job_name => 'generate_points',
        job_type => 'STORED_PROCEDURE',
        job_action => 'GEN_POINT',
        repeat_interval => 'FREQ=SECONDLY; INTERVAL=1',
        end_date => SYSTIMESTAMP + INTERVAL '30' SECOND,
        enabled => TRUE
    );
END;