Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric A heap is a table without a clustered index. One or more nonclustered indexes can be created on tables stored as a heap. Data is stored in the heap without specifying an order. Usually ...
使用以下 SQL 语句来检查碎片程度: SELECTdbschemas.[name]AS[SchemaName],dbtables.[name]AS[TableName],indexes.[name]AS[IndexName],indexstats.[avg_fragmentation_in_percent]FROMsys.dm_db_index_physical_stats(DB_ID(),NULL,NULL,NULL,NULL)ASindexstatsINNERJOINsys.tablesASdbtablesONindexstats.[object_...
CREATECLUSTEREDINDEXIX_EmployeeIDONEmployee(EmployeeID); 1. 这将使Employee表不再是 Heap,而是变为一个有聚集索引的表。 步骤6: 删除聚集索引,验证 Heap 表的失效状态 我们还需观察失效状态,因此,我们可以删除聚集索引并验证: DROPINDEXIX_EmployeeIDONEmployee; 1. 删除后,再次运行步骤 3 的查询,确认Employee...
通过下面的 SQL 查询数据库的索引碎片 SELECT OBJECT_NAME(ind.OBJECT_ID) AS TableName, ind.name AS IndexName, indexstats.index_type_desc AS IndexType, indexstats.avg_fragmentation_in_percent FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, NULL) indexstats INNER JOIN sys.i...
实际上,您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)。下面,我们举例来说明一下聚集索引和非聚集索引的区别: 其实,我们的汉语字典的正文本身就是一个聚集索引。比如,我们要查“...
XMLA shredded, and persisted, representation of the XML binary large objects (BLOBs) in thexmldata type column.XML Indexes (SQL Server) Full-textA special type of token-based functional index that is built and maintained by the Microsoft Full-Text Engine for SQL Server. It provides efficient ...
SQL Server 中的索引以 B-Tree 的形式存储,例如以下图: 建立聚集索引(clustered index)来改进性能 RDBMS 随着数据的增长都会面临查询性能的下降,索引就是专门设计来解决问题的。聚集索引是全部索引的基础。没有它数据表就是一个堆(heap)。聚集索引决定了数据的物理存储形态,所以一张表上仅仅能有一个聚集索引。
gäller för:SQL ServerAzure SQL DatabaseAzure SQL Managed InstanceAzure Synapse AnalyticsAnalytics Platform System (PDW) Skapar ett relationsindex i en tabell eller vy. Kallas även för ett radlagringsindex eftersom det antingen är ett grupperat eller icke-grupperat B-trädindex. Du ...
Applies to: SQL Server Azure SQL Database Azure SQL Managed InstanceA heap is a table without a clustered index. One or more nonclustered indexes can be created on tables stored as a heap. Data is stored in the heap without specifying an order. Usually data is initially stored in the ...
Modifies an existing table or view index (rowstore, columnstore, or XML) by disabling, rebuilding, or reorganizing the index; or by setting options on the index. Transact-SQL syntax conventions Syntax Syntax for SQL Server, Azure SQL Database, and Azure SQL Managed Instance. syntaxsql Copy ...