索引 可以把索引理解为一种特殊的目录。微软的SQL SERVER提供了两种索引:聚集索引(clustered index,也称聚类索引、簇集索引)和非聚集索引(nonclustered index,也称非聚类索引、非簇集索引)。 聚集索引和非集聚索引 聚集索引:该索引中键值的逻辑顺序决定了表中相应行的物理顺序。 非聚集索引:该索引中索引的逻辑顺序与...
统一盘区 Uniform Extents:一个区中的8个页对应一个对象 索引(Index) 通过上面我们已经知道,索引也是存储在页上的,具有聚集索引(Clustered Index)的表是以B-tree(不是B减树。。。)结构组织的且数据按聚集索引顺序存储,否则存储在堆(Heap)上。B树上每一页称为一个索引节点,其中包含: 根节点:顶端节点,包含存有...
createuniqueclusteredindexidx_uqe_clu_stu_name_age onstudent(name, age); if(exists(select*fromsys.indexeswherename ='idx_cid')) dropindexstudent.idx_cid go if(exists(select*fromsys.indexeswherename ='idx_cid')) dropindexstudent.idx_cid go --非聚集索引 createnonclusteredindexidx_cid on st...
SET STATISTICS IO ON -- Turn Graphical Showplan ON (Ctrl+K) USE CREDIT go -- 逻辑读取144 次 Clustered Index Scan SELECT m.LastName, m.FirstName, m.Phone_No FROM dbo.Member AS m WITH (INDEX (0)) WHERE m.LastName LIKE '[S-Z]%' go --CREATE INDEX MemberLastName ON Member(LastNa...
而索引扫描中又可分为索引全扫描(index full scan)、索引范围扫描(index range scan)和索引唯一扫描(index unique scan)等。 2.sql server中clustered index scan,table scan,index scan 在sqlserver中也有类似的内容,这里就要将的是table scan,index scan以及index seek. ...
CREATE UNIQUE NONCLUSTERED INDEX IX_person2_UserID ON person2 (UserID) 3. 查看索引的级数 使用DMV来查看所有的索引分布。 SELECT index_depth, index_level, record_count, page_count, min_record_size_in_bytes as 'MinLen', max_record_size_in_bytes as 'MaxLen', ...
A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value. The pointer from an index row in a nonclustered index to a data row is called a row locator. The structure of the ...
index_handle, column_id; GO 应尽可能将缺少的索引建议与当前数据库中的现有索引组合在一起。 了解如何在 优化缺少索引建议的非聚集索引时应用这些建议。 参考 https://learn.microsoft.com/zh-cn/sql/relational-databases/indexes/tune-nonclustered-missing-index-suggestions?view=sql-server-ver16 https://...
The last part of the confusion is around what effect rebuilding an index has on other indexes. The answer is always that rebuilding an index only affects that particular index and its statistics. The exception is for a non-unique clustered index in SQL Server 2000, where rebuilding such an ...
CREATETABLEmytable2(C1INT,C2INT,C3INT,C4INT,C5INT)GOCREATECLUSTEREDINDEXIC1ONmytable2(C1)CREATEINDEXIC2ONmytable2(C2)CREATEINDEXIC3ONmytable2(C3)CREATEINDEXIC4ONmytable2(C4)CREATEINDEXIC5ONmytable2(C5)GODECLARE@NINT=1WHILE@N<1000000BEGINDECLARE@N1INT=RAND()*4500DECLA...