title: mysql stored-procedure: out parameter
body: <p>I have a mysql stored procedure from this (<a href="http://books.google.com/books?id=YpeP0ok0cO4C&amp;printsec=frontcover" rel="noreferrer">google book</a>), and one example is this:</p>
  
  <pre><code>DELIMITER $$
  
  DROP PROCEDURE IF EXISTS my_sqrt$$
  CREATE PROCEDURE my_sqrt(input_number INT, OUT out_number FLOAT)
  BEGIN
      SET out_number=SQRT(input_number);
  END$$
  
  DELIMITER ;
  </code></pre>
  
  <p>The procedure compiles fine. (I am using MySQL Query Browser in ubuntu).</p>
  
  <p>However when I call the procedure:</p>
  
  <pre><code>CALL my_sqrt(4,@out_value);
  </code></pre>
  
  <p>(also in query browser)</p>
  
  <p>It returns an error:</p>
  
  <pre><code>(1064) check the manual that correspond to the...
  </code></pre>
  
  <p>Why isn't this example working?</p>