SQL SERVER2005学习笔记（一）:索引

SQL SERVER2005学习笔记（一）:索引

1.未指定order by子句时，查询结果受到检索时使用到的索引影响；

SELECT TOP 10000 IDENTITY(INT ,1,1) AS Pkid ,o.* INTO tempTable FROM sys.objects o,sys.[columns] c

CREATE  CLUSTERED INDEX ixuc_pkid ON tempTable(pkid ASC)
--CREATE  CLUSTERED INDEX ixuc_pkid ON tempTable(pkid DESC)

DROP INDEX dbo.tempTable.ixuc_pkid

(1) SELECT * FROM tempTable tt

CREATE INDEX cxde_objid ON dbo.tempTable(OBJECT_ID)

(2) SELECT * FROM tempTable tt ORDER BY tt.OBJECT_ID

DROP INDEX dbo.tempTable.ixuc_pkid

(3) SELECT * FROM tempTable tt ORDER BY tt.OBJECT_ID

通过CTRL+L查看(1)(2)(3)查询开销验证以上结论

2.指定order by子句时,除非受到