trigger blank in MySQL

DELIMITER $$
CREATE TRIGGER triger_name
      trigger_time trigger_event ON table_name FOR EACH ROW
      BEGIN
      END;

$$

DELIMITER ;

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DELIMITER $$
CREATE TRIGGER prevent_self_follows
      BEFORE INSERT ON follows FOR EACH ROW
      BEGIN
         IF NEW.follower_id = NEW.followee_id
         THEN
            SIGNAL SQLSTATE '45000'
            SET MESSAGE_TEXT = 'You cannot follow yourself!';
          END IF;
      END;

$$

DELIMITER ;


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DELIMITER $$
CREATE TRIGGER capture_unfollows
      AFTER DELETE ON follows FOR EACH ROW
      BEGIN
         INSERT INTO unfollows(follower_id, followee_id)
         VALUES(OLD.follower_id, OLD.followee_id);
      END;

$$

DELIMITER ;

##############################################################
DELIMITER $$
CREATE TRIGGER update_automatically_staff_table_orders_served
      AFTER INSERT ON customer_orders FOR EACH ROW
      BEGIN
          UPDATE staff
          SET orders_served = orders_served + 1
          WHERE staff.staff_id = NEW.staff_id;
      END;

$$

DELIMITER ;