code: private function compileOn(array $join)
  	{
  		$sql = array();
  		list($on, $table, $type, $c1, $op, $c2) = $join;
  
  		if ($type !== null)
  		{
  			$sql[] = $type;
  		}
  
  		array_push($sql, "JOIN", $table, "ON", $c1, $op, $c2);
  		return join(' ', $sql);
  	}
docs: Compiles an ON join.
  
  @param  array $join  The on join to compile
  @return string