To create a non-clustered index, you have to use the “CREATE NONCLUSTERED” statement. The rest of the syntax remains the same as the syntax for creating a clustered index. The following script creates a non-clustered index “IX_tblPatient_Name” which sorts the records in ascending order ...
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"...
4. 这里因为是建了聚集索引,表数据存储在索引的叶子节点,所以应用的clustered index scan,读取的行数还是100W,所有实际执行的行数为1行。 非聚集索引下WHERE查询 --在NAME字段上建立非聚集索引。 CREATE NONCLUSTERED INDEX IX_EMP_NAME ON EMPLOYEES(NAME) -- 再次执行WHERE查询并含实际执行计划。 SELECT * FROM...
1. 什么是聚合索引(clustered index) / 什么是非聚合索引(nonclustered index)? 2. 聚合索引和非聚合索引有什么区别? 深入浅出理解索引结构 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...
Nonclustered Nonclustered indexes have a structure separate from the data rows. 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 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 ...
要监控和调优SQL Server中的非聚集索引以提升查询性能,可以遵循以下步骤: 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 + ...
When you create a UNIQUE constraint, a unique nonclustered index is created to enforce a UNIQUE constraint by default. You can specify a unique clustered index if a clustered index on the table doesn't already exist. An index created as part of the constraint is automatically given the same...
Using SQL Server Management Studio To create a nonclustered index by using the Table Designer In Object Explorer, expand the database that contains the table on which you want to create a nonclustered index. Expand theTablesfolder. Right-click the table on which you want to create a nonclust...
When you create a UNIQUE constraint, a unique nonclustered index is created to enforce a UNIQUE constraint by default. You can specify a unique clustered index if a clustered index on the table doesn't already exist. An index created as part of the constraint is automatically given the same...