在前面的查询中,SQL Server 读取根节点页并检索每个叶节点页和行以进行数据检索。 现在让我们在 SQL Server的EmpContactNumber列上的Employee表上 创建一个唯一的非聚集索引作为索引键: CREATEUNIQUENONCLUSTERED INDEX IX_NonClustered_EmployeeONdbo.Employee(EmpContactNumber); 1 在我们解释这个索引之前,重新运行 SEL...
After a unique clustered index has been created on a view, nonclustered indexes can be created. For more information, seeCreate indexed views. Security Permissions Requires ALTER permission on the table or view. User must be a member of thesysadminfixed server role or thedb_ddladminanddb_owner...
After a unique clustered index has been created on a view, nonclustered indexes can be created. For more information, seeCreate indexed views. Security Permissions Requires ALTER permission on the table or view. User must be a member of thesysadminfixed server role or thedb_ddladminanddb_owner...
for a nonclustered index is 1700 bytes. The index 'ind_hname' has maximum length of 4000 bytes. For some combination of large values, the insert/update operation will fail. create index ind_hname on t1(hid) include(hname) --不报错,正常创建,索引键列是hid,包含列是hname 官方文档的说法:...
一、CREATE INDEX语法 CREATE INDEX语句所做的事情与其听上去一样-用于在指定表或视图上基于声明的列创建索引: CREATE [UNIQUE] [CLUSTERED | NONCLUSTERED] INDEX <index name> ON (<column name> [ASC|DESC][,...n]) INCLUDE (<column name> [,...n]) [ WITH [PAD_INDEX =...
CREATE NONCLUSTERED --再重新建过一次,这次我们INCLUDE Age列 INDEX Index_Name ON Person(Name) INCLUDE (Age) 1. 2. 3. 4. 5. 现在我们再来看看刚才的查询的执行计划: 由于Age列也被INCLUDE进了非聚集索引INDEX_Name中,因此这次仅仅通过查找非聚集索引就能够得到所需的全部数据。不需要再扫描聚集索引了。明...
CREATE CLUSTERED INDEX Index_Name ON Person(Name) --再在重建Name列聚集索引 1. 2. 3. 4. 再执行查询语句: select top 3 * from Person 1. 输出结果如下: 留意到同样的语句,返回已经改变。可以聚集索引是表的顺序,会影响到top语句。 5、导航树 ...
1. 首先,创建一张表格,上面有一个clustered index,两个non-clustered index。 create table tt(id int identity primary key,a char(36),b char(36),d varchar(max)) go create index ix_a_bc on tt(a)include(d) create index ix_b_cd on tt(b)include(d) ...
编写 CREATE INDEX DDL 语句以实现缺失索引时,首先在 CREATE INDEX 语句的 ON 子句中列出相等列,然后列出相等列。 应该在 CREATE INDEX 语句的 INCLUDE 子句中列出包含列。 若要确定相等列的有效顺序,请基于其选择性排序,首先列出选择性最强的列(列列表中的最左侧)。 了解如何 应用缺失索引建议。 示例 以下示例...
Include nonkey columns in a nonclustered index to avoid exceeding the current index size limitations of a maximum of 32 key columns and a maximum index key size of 1,700 bytes (16 key columns and 900 bytes prior to SQL Server 2016 (13.x)). The Database Engine doesn't consider nonkey...