public function _sqlite_increment_trigger($pkey) {
        $table = $this->db->quotekey($this->name);
        $pkey = $this->db->quotekey($pkey);
        $triggerName = $this->db->quotekey($this->name.'_insert');
        $queries[] = "DROP TRIGGER IF EXISTS $triggerName;";
        $queries[] = 'CREATE TRIGGER '.$triggerName.' AFTER INSERT ON '.$table.
                     ' WHEN (NEW.'.$pkey.' IS NULL) BEGIN'.
                     ' UPDATE '.$table.' SET '.$pkey.' = ('.
                     ' select coalesce( max( '.$pkey.' ), 0 ) + 1 from '.$table.
                     ') WHERE ROWID = NEW.ROWID;'.
                     ' END;';
        return $queries;
    }