A Little Noise

Trigger on firing table

CREATE TABLE t1 (id int);
CREATE TRIGGER t1_ai AFTER INSERT ON t1 FOR EACH ROW
  INSERT INTO t1 VALUES (NEW.id);

That's not allowed; it won't let you create the trigger.

CREATE TABLE t1 (id int);
CREATE TABLE f1 (id int) ENGINE=FEDERATED CONNECTION='localhost/test/t1';
CREATE TRIGGER t1_ai AFTER INSERT ON t1 FOR EACH ROW
  INSERT INTO f1 VALUES (NEW.id);

The server lets that through. Don't do it.