ig_triggers.sql

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 be a follower of Yourself';
		END IF;
	END;

CREATE TRIGGER logs_unfollowEvent
	AFTER DELETE ON follows FOR EACH ROW
	BEGIN
		INSERT INTO unfollows(follower_id,followee_id) VALUES (OLD.follower_id, OLD.followee_id); -- INSERT INTO unfollows SET follower_id = OLD.follower_id, followee_id = OLD.followee_id;
	END;

$$

DELIMITER ;