title: SQL constraint on values does not work
body: <p>I'm trying to constrict a column to specific values, with no luck.<br>
  Here's what I have been trying:  </p>
  
  <pre><code>mysql&gt; CREATE TABLE my_table (
      -&gt; name VARCHAR(20),
      -&gt; sex CHAR(1) CHECK (sex IN('F','M'))
      -&gt; );
  Query OK, 0 rows affected (0.18 sec)
  
  mysql&gt; INSERT INTO my_table VALUES
      -&gt; ('John','D');
  Query OK, 1 row affected (0.07 sec)
  
  mysql&gt; SELECT * FROM my_table;
  +------+------+
  | name | sex  |
  +------+------+
  | John | D    |
  +------+------+
  1 row in set (0.00 sec)
  
  mysql&gt; 
  </code></pre>
  
  <p>as you can see, the constraint was not enforced...</p>