title: MySQL foreign keys doesn't cause child table to populate
body: <p>I'm trying to create relationships in MySQL using forein keys. Everytime I successfully create the forien key, but when I describe the table, the key is considered "MUL". After inserting some records into the parent table, I get null values in the child. I've been researching this for hours and have come up empty handed. I even checked the innodb status and have no foreign key error reports. I'm not entirely sure why I'm getting null values, but I'm assuming its because of the "MUL" key value. Can someone confirm this and try and help me out?</p>
  
  <pre><code>create table employee
  ( id int
  , first varchar(128)
  , last varchar(128)
  , primary key(id)
  ) engine=innodb; 
  
  create table borrow
  (ref auto_increment
  , empID int
  , book varchar(128)
  , primary key(ref) 
  ) engine=innodb; 
  
  alter table borrow add constraint fk_borrow
    foreign key (empID) references employee(id);
  
  insert into borrow (empID, book) values (1,'mike');
  </code></pre>