根據系統(tǒng)示例用戶數據庫提供的pubs表,閱讀下列程序,說明其功能。 USE pubs GO WHILE (SELECT AVG(price) FROM titles) < $30 BEGIN UPDATE titles SET price = price * 2 SELECT MAX(price) FROM titles IF (SELECT MAX(price) FROM titles) > $50 BREAK ELSE CONTINUE END PRINT ‘Too much for the market to bear’