drupal intsall module trouble

please verify my below code, my drupal is D6, Not creating table as well not deleting tables.

<?php
// custom1.install

function custom1_install() {
  switch ($GLOBALS['db_type']) {
    case 'mysql':
    case 'mysqli':
      db_query("CREATE TABLE IF NOT EXISTS block_quiz_customer_ans (
        crid int(30) NOT NULL AUTO_INCREMENT,
        qid int(30) NOT NULL,
        cust_ans varchar(255) NOT NULL,
        cust_ip varchar(255) NOT NULL,
        cust_res_date_time varchar(255) NOT NULL,
        created varchar(50) NOT NULL,
        status tinyint(20) NOT NULL DEFAULT '1',
        PRIMARY开发者_Python百科 KEY (`crid`)
        ) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=0;");
      break;
  }
}

function custom1_uninstall() {
  print "This is uninstall";
  drupal_uninstall_schema('block_quiz_customer_ans');
  variable_del('block_quiz_customer_ans');
}

Use schema instead of mysql queries for the install file of a module.

function custom1_install(){
$schema['table_name'] = array(
    'description' => '<description',
    'fields' => array(
      'field_name' => array(
        'description' => '<description>',
        'type' => '<datatype>',
      ),
    ),
    'primary key' => array('<field_name>'),
  );
return $schema;

}

Hope this helps!!