查看执行计划我们可以看到,虽然逻辑读的执行次数没有变化仍为 303,但是查找操作已经被优化为非聚集索引查找(Non-Clustered Index Seek)。 另一种改善方式是调整索引中的列顺序: drop INDEX [IX_MySalesOrderDetail_OrderQty_ProductID] ON [dbo].[MySalesOrderDetail] CREATE NONCLUSTERED INDEX [IX_MySalesOrderDetai...
--建立两个非聚集索引,一个在Name列,一个在INSiteId列 CREATE NONCLUSTERED INDEX INDEX_Name ON Person(Name) INCLUDE(Age) --索引还是刚才的索引,但是包含多一列 CREATE NONCLUSTERED INDEX INDEX_INSiteId ON Person(INSiteId) INCLUDE(Height) --同上 SELECT Name,Age,Height,INSiteId FROM Person WHERE INS...
CREATEUNIQUENONCLUSTERED INDEX IX_NonClustered_EmployeeONdbo.Employee(EmpContactNumber); 1 在我们解释这个索引之前,重新运行 SELECT 语句并查看实际的执行计划: 在这个执行计划中,我们可以看到两个组件: 索引查找(非聚集) - Index Seek(NonClustered) 键查找(集群) - Key Lookup(Clustered) 要了解这些组件,我们...
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,非聚集索引的include 非聚集索引的Include属性可以让非聚集索引包含其他列。如 CREATENONCLUSTEREDINDEX[NonIxUser]ON[dbo].[Users]([NAME]ASC) INCLUDE ([ID],[CreatTime])GO 这表语句就是在Name列的非聚集索引上添加ID,和CreateTime列。 在上一个介绍中,我们知道在查询NAME = '张三180' 时,会出现RID,...
Index independent of a constraint By default, a nonclustered index is created if clustered is not specified. The maximum number of nonclustered indexes that can be created per table is 999. This includes any indexes created by PRIMARY KEY or UNIQUE constraints, but does not include XML indexes...
Index independent of a constraint By default, a nonclustered index is created if clustered is not specified. The maximum number of nonclustered indexes that can be created per table is 999. This includes any indexes created by PRIMARY KEY or UNIQUE constraints, but does not include XML indexes...
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) ...
1. 使用sys.dm_db_index_usage_stats动态管理视图来查看索引的使用情况。例如,可以使用以下查询来查看最近使用的非聚集索引: SELECT OBJECT_NAME(s.[object_id]) AS TableName, i.name AS IndexName, i.index_id, ius.user_seeks + ius.user_scans + ius.user_lookups AS TotalUsage FROM sys.dm_db_ind...
CREATE NONCLUSTERED INDEX IX_Address_PostalCode ON Person.Address (PostalCode) INCLUDE (AddressLine1, AddressLine2, City, StateProvinceID); GO Related content CREATE INDEX (Transact-SQL) SQL Server and Azure SQL index architecture and design guideFeed...