Datamodeling part I

gistfile1.txt

-- 1. create the function
CREATE OR REPLACE FUNCTION log_post_update()
RETURNS TRIGGER AS $$
BEGIN
  NEW.updated_at = NOW();

  IF NEW.title <> OLD.title THEN
    INSERT INTO posts_logs (post_id, log_message)
    VALUES (NEW.id, 'Updated title');
  ELSEIF NEW.description <> OLD.description THEN
    INSERT INTO posts_logs (post_id, log_message)
    VALUES (NEW.id, 'Updated description');
  END IF;

  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- 2. create the trigger that is calling our function
CREATE TRIGGER post_update_trigger
AFTER UPDATE ON posts
FOR EACH ROW
EXECUTE FUNCTION log_post_update();