Can I add to an existing Entity schema from my own custom module I'm extending a the Quiz module; by having taking extra data regarding the test .   For this I have a custom module that redirects using a custom form .

It all works fine but as its only a single value I'd like to just add it to the existing 'Quiz result' entity.  I know how to do this by hacking the 'contrib' module 
OPEN 'quiz.install' and adding it to the $schema['quiz_node_results'] array.  

Once its added here I can then see it in Views as needed.  But obviously this solution isn't good enough.  Is there a way to add to an existing Entity schema from my own custom module; rather making a separate table in SQL for this info. 

I've tried hook_schema_alter as well, but can't seem to get that to work either. 

Here's what I had in my my_module.install file

 function my_module_schema_alter() {
  $schema = array();
  // Create the quiz node results table
  $schema['quiz_node_results']['fields']['time_taken'] = array(
    'type' =&gt; 'int',
    'size' =&gt; '10',
    'not null' =&gt; TRUE,
    'default' =&gt; 0,
    'description' =&gt; 'Stores the user inputted estimated time.',
  );
}


function my_module_install() {
  $ret = array();
  $schema['quiz_node_results'] = array();
  rcni_saq_extended_schema_alter($schema);
   foreach ($schema['quiz_node_results']['fields'] as $name =&gt; $spec) {
    db_add_field($ret, 'quiz_node_results', $name, $spec);
  }
}


Many thanks for any help.
your my_module_schema_alter is missing a schema parameter.

fixed:

function my_module_schema_alter(&amp;$schema) {
  $schema = array();
  // Create the quiz node results table
  $schema['quiz_node_results']['fields']['time_taken'] = array(
    'type' =&gt; 'int',
    'size' =&gt; '10',
    'not null' =&gt; TRUE,
    'default' =&gt; 0,
    'description' =&gt; 'Stores the user inputted estimated time.',
  );
}