SQL 2005 tips

USE tempdb
GO
CREATE TABLE AuctionItems
(
  itemid       INT          NOT NULL PRIMARY KEY NONCLUSTERED,
  itemtype     NVARCHAR(30) NOT NULL,
  whenmade     INT          NOT NULL,
  initialprice MONEY        NOT NULL,
  /* other columns */
)
--ÏîÄ¿ÀàÐÍ¡¢ÏîÄ¿µÄÖÆÔìÈÕÆÚÒÔ¼°ËüµÄ³õʼ¼Û¸ñ¡£Ö»ÓÐÓëËùÓÐÏîÄ¿ÓйصÄÊôÐÔ±»´æ´¢ÔÚAuctionItems
CREATE UNIQUE CLUSTERED INDEX idx_uc_itemtype_itemid
  ON AuctionItems(itemtype, itemid)
INSERT INTO AuctionItems VALUES(1, N'Wine',     1822,      3000)
INSERT INTO AuctionItems VALUES(2, N'Wine',     1807,       500)
INSERT INTO AuctionItems VALUES(3, N'Chair',    1753,    800000)
INSERT INTO AuctionItems VALUES(4, N'Ring',     -501,   1000000)
INSERT INTO AuctionItems VALUES(5, N'Painting', 1873,   8000000)
INSERT INTO AuctionItems VALUES(6, N'Painting', 1889,   8000000)
 
--ÆäËûÊôÐÔÌض¨ÓÚÏîÄ¿ÀàÐÍ£¬²¢ÇÒ²»Í¬ÀàÐ͵ÄÐÂÏîÄ¿±»²»¶ÏµØÌí¼Ó¡£ÕâÑùµÄÊôÐÔ¿ÉÒÔ´æ´¢ÔÚ²»Í¬µÄItemAttributes ±íÖУ¬ÆäÖÐÿ¸öÏîÊôÐÔ¶¼´æ´¢ÔÚ²»Í¬µÄÐÐÖС£Ã¿¸öÐж¼°üº¬ÏîÄ¿ID¡¢ÊôÐÔÃû³ÆºÍÊôÐÔÖµ
CREATE TABLE ItemAttributes
(
  itemid    INT          NOT NULL REFERENCES AuctionItems,
 
  attribute NVARCHAR(30) NOT NULL,
  value     SQL_VARIANT  NOT NULL,
  PRIMARY KEY (itemid, attribute)
)
INSERT INTO ItemAttributes
  VALUES(1, N'manufacturer', CAST(N'ABC'              AS NVARCHAR(30)))
INSERT INTO ItemAttributes
  VALUES(1, N'type',