title: What is MySQL's default ON DELETE behavior?
body: <p>I'm trying to parse the MySQL <a href="http://dev.mysql.com/doc/refman/5.0/en/innodb-foreign-key-constraints.html" rel="noreferrer">docs</a>. They could be clearer. What they seem to be saying is that there are five possibilities: SET NULL, NO ACTION, RESTRICT, CASCADE, and SET DEFAULT.</p>
  
  <p>NO ACTION and RESTRICT do the same thing (prevent any DB change that breaks an FK) and that thing is the default so if you omit an ON DELETE clause you're saying NO ACTION (or RESTRICT -- same thing).</p>
  
  <p>SET NULL allows a parent row deletion, sets the FK to NULL.</p>
  
  <p>CASCADE deletes child row.</p>
  
  <p>SET DEFAULT should just never be used.</p>
  
  <p>Is this more or less correct?</p>