title: Add foreign key on delete cascade phpMyAdmin is not working
body: <p>I have a main table called <code>book</code> with fields <code>id_book</code> (primary, unique, auto increment) and <code>name</code>.
  I have a secondary table called <code>tag</code> with fields <code>book_id</code> and <code>tag</code></p>
  <p>Each book can have many tags. I want that when I delete a book, all the tags to be deleted as well.</p>
  <p>I tried this with this:</p>
  <pre><code>ALTER TABLE tag
  ADD FOREIGN KEY (book_id)
  REFERENCES book(id_book) 
  ON UPDATE CASCADE
  ON DELETE CASCADE
  </code></pre>
  <p>I know I used this block of SQL in the past on some other project and it worked but now it seems it is not working anymore and I don't know why. If I delete a book, the tags will not be deleted.</p>