title: Delete all entries that have a certain field
body: <p>I have a database table that has 4 fields. It is created like this:</p>
  
  <pre><code>CREATE TABLE meta (
        meta_id bigint(20) NOT NULL auto_increment,
        object_id bigint(20) NOT NULL default '0',
        meta_key varchar(255) default NULL,
        meta_value longtext,
        PRIMARY KEY (`meta_id`),
        KEY `object_id` (`object_id`),
        KEY `meta_key` (`meta_key`)
      )
  </code></pre>
  
  <p>How can I delete all entries from this table, that have a certain <code>meta_key</code>, for eg. <code>foo</code> ?</p>