Create table posts (
post_id Int(10) NOT NULL AUTO_INCREMENT,
author_id Char(36) NOT NULL,
Primary Key (post_id)) ENGINE = InnoDB;

Create table users (
id Char(36) NOT NULL,
username Varchar(16),
Primary Key (id)) ENGINE = InnoDB;

Alter table posts add Constraint rel_post_author Foreign Key (author_id) references users (id) on delete restrict on update restrict;