How to include attributes of the MySQL table to hook_schema() schema in drupal 7?
You can't use an ON UPDATE unfortunately - Drupal's schema API doesn't give you that sort of dbms-specific control.

You can use unsigned for unsigned and default for a default value though:

$schema['some_table'] = array(
  'fields' =&gt; array(
    'some_field' =&gt; array(
      'type' =&gt; 'int',
      'not null' =&gt; TRUE,
      'unsigned' =&gt; TRUE,
      'default' =&gt; 0,
    ),
  ),
);


See the Schema API docs for the full list of data types and usage.