title: Alter table to give foreign key constraint
body: <p>I have a table which  has 2 columns which I copied from two different tables.What I want to do now is give a foreign key constraint on both the column names email and id shown below.</p>
  
  <pre><code>ALTER TABLE users_role_map
  ADD CONSTRAINT FK_users_role_map
  FOREIGN KEY (email) REFERENCES usert(email),
  FOREIGN KEY (id) REFERENCES rolet(id)
  ON UPDATE CASCADE
  ON DELETE CASCADE;
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
  corresponds to your MySQL server version for the right syntax to use near 'FOREI
  GN KEY (id) REFERENCES rolet(id)
  ON UPDATE CASCADE
  ON DELETE CASCADE' at line 4
  </code></pre>