title: INSERT ... ON DUPLICATE KEY (do nothing)
body: <p>I have a table with a unique key for two columns:</p>
  
  <pre><code>CREATE  TABLE `xpo`.`user_permanent_gift` (
  `id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `fb_user_id` INT UNSIGNED NOT NULL ,
  `gift_id` INT UNSIGNED NOT NULL ,
  `purchase_timestamp` TIMESTAMP NULL DEFAULT now() ,
  PRIMARY KEY (`id`) ,
  UNIQUE INDEX `user_gift_UNIQUE` (`fb_user_id` ASC, `gift_id` ASC) );
  </code></pre>
  
  <p>I want to insert a row into that table, but if the key exists, to do nothing! I don't want an error to be generated because the keys exist.</p>
  
  <p>I know that there is the following syntax:</p>
  
  <pre><code>INSERT ... ON DUPLICATE KEY UPDATE ...
  </code></pre>
  
  <p>but is there something like:</p>
  
  <pre><code>INSERT ... ON DUPLICATE KEY DO NOTHING 
  </code></pre>
  
  <p>?</p>