CREATE TABLE a (
  id int NOT NULL,
  val int NOT NULL,

  PRIMARY KEY (id)
) ENGINE=InnoDB;


CREATE TABLE a2 (
  id int NOT NULL,
  val char(3) DEFAULT NULL COMMENT 'Can be null',

  FOREIGN KEY (id) REFERENCES a (id)
) ENGINE=InnoDB;


CREATE TABLE a3 (
  id int NOT NULL,
  val int DEFAULT NULL COMMENT 'Can be null',

  FOREIGN KEY (id) REFERENCES a (id)
) ENGINE=InnoDB;


CREATE TABLE d (id int, val int);


CREATE TABLE e (
  id int ,
  val int
);


