title: Insert GENERATED ALWAYS as in SQL
body: <p>I created a table like this:</p>
  
  <pre><code>CREATE TABLE `group` (
    `g_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
    `owner_id` int(10) unsigned NOT NULL,
    `g_name` varchar(45) NOT NULL,
    `refer_code` varchar(45) GENERATED ALWAYS AS (concat(`g_name`)) VIRTUAL,
    `created_on` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
    `row_hash` varchar(256) NOT NULL,
    PRIMARY KEY (`g_id`),
    UNIQUE KEY `g_hash_UNIQUE` (`row_hash`),
    UNIQUE KEY `refer_UNIQUE` (`refer_code`),
    KEY `owner_idx` (`owner_id`),
    CONSTRAINT `owner_id` FOREIGN KEY (`owner_id`) REFERENCES `user` (`u_id`) ON DELETE CASCADE ON UPDATE CASCADE
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
  </code></pre>
  
  <p>The update statement gives me error:</p>
  
  <pre><code>INSERT INTO `server`.`group` (`owner_id`, `g_name`, `refer_code`, `created_on`, `row_hash`) 
  VALUES ('4', 'cool', null, '2018-02-13 10:34:11', '452345324')
  </code></pre>
  
  <blockquote>
    <p>Error Code: 3105. The value specified for generated column 'refer_code' in table 'group' is not allowed.  </p>
  </blockquote>
  
  <p>How to specify the <code>refer_code</code> while inserting?</p>