code: public function compile()
  	{
  		if (empty($this->clauses))
  		{
  			return "";
  		}
  
  		$sql = array();
  		foreach ($this->clauses as $clause)
  		{
  			list($type, $column, $op, $value, $isParam) = $clause;
  			$sql[] = $type;
  			$sql[] = "{$column} {$op}";
  
  			$sql[] = $isParam ? "?" : $value;
  
  			$this->params[] = $value;
  		}
  
  		array_shift($sql);
  
  		return $this->getType()." ".join(" ", $sql);
  	}
docs: Compiles the query into raw SQL
  
  @return  string