The number of rows on an intermediate index page is never less than two, regardless of how low the value of fillfactor. Specifies a percentage that indicates how full the Database Engine should make the leaf level of each index page during index creation or rebuild. The value for fillfactor must be an integer value from 1 to Fill factor values 0 and are the same in all respects. If fillfactor is , the Database Engine creates indexes with leaf pages filled to capacity. The Database Engine does not dynamically keep the specified percentage of empty space in the pages.
For more information, see Specify Fill Factor for an Index. Specifies whether to store temporary sort results in tempdb. ON The intermediate sort results that are used to build the index are stored in tempdb. This may reduce the time required to create an index if tempdb is on a different set of disks than the user database.
However, this increases the amount of disk space that is used during the index build. In addition to the space required in the user database to create the index, tempdb must have about the same amount of additional space to hold the intermediate sort results. Specifies the error response when an insert operation attempts to insert duplicate key values into a unique index.
The default is OFF. ON A warning message will occur when duplicate key values are inserted into a unique index. Only the rows violating the uniqueness constraint will fail. OFF An error message will occur when duplicate key values are inserted into a unique index. Disabling automatic recomputation of distribution statistics may prevent the query optimizer from picking optimal execution plans for queries involving the table.
When ON , the statistics created are per partition statistics. If per partition statistics are not supported the option is ignored and a warning is generated. Incremental stats are not supported for following statistics types:. Is an option to drop and rebuild the existing clustered or nonclustered index with modified column specifications, and keep the same name for the index.
SQL Server displays an error if the specified index name already exists. Specifies whether underlying tables and associated indexes are available for queries and data modification during the index operation. ON Long-term table locks are not held for the duration of the index operation.
During the main phase of the index operation, only an Intent Share IS lock is held on the source table. This enables queries or updates to the underlying table and indexes to proceed. At the start of the operation, a Shared S lock is held on the source object for a very short period of time. At the end of the operation, for a short period of time, an S Shared lock is acquired on the source if a nonclustered index is being created. A Sch-M Schema Modification lock is acquired when a clustered index is created or dropped online and when a clustered or nonclustered index is being rebuilt.
OFF Table locks are applied for the duration of the index operation. An offline index operation that creates, rebuilds, or drops a clustered index, or rebuilds or drops a nonclustered index, acquires a Schema modification Sch-M lock on the table.
This prevents all user access to the underlying table for the duration of the operation. An offline index operation that creates a nonclustered index acquires a Shared S lock on the table. For more information, see Perform Index Operations Online.
Indexes, including indexes on global temp tables, can be created online except for the following cases:. Indicates time an integer value specified in minutes that a resumable online index operation is executed before being paused. For more detailed information about index operations that can be performed online, see Guidelines for Online Index Operations. ON Row locks are allowed when accessing the index.
The Database Engine determines when row locks are used. ON Page locks are allowed when accessing the index. The Database Engine determines when page locks are used. Specifies whether or not to optimize for last-page insert contention. See the Sequential Keys section for more information. Overrides the max degree of parallelism configuration option for the duration of the index operation. For more information, see Configure the max degree of parallelism Server Configuration Option.
The maximum is 64 processors. For more information, see Configure Parallel Index Operations. Specifies the data compression option for the specified index, partition number, or range of partitions.
The options are as follows:. For more information about compression, see Data Compression. The sort operation may be eliminated in some situations. Indexes can be created on a temporary table.
When the table is dropped or the session ends, the indexes are dropped. A clustered index can be built on a table variable when a Primary Key is created. When the query completes or the session ends, the index is dropped. Creating a clustered index on a table heap or dropping and re-creating an existing clustered index requires additional workspace to be available in the database to accommodate data sorting and a temporary copy of the original table or existing clustered index data.
If you first create a nonclustered index on a table stored as a heap or clustered index, the index will persist if you later convert the table to a clustered columnstore index. It is also not necessary to drop the nonclustered index when you rebuild the clustered columnstore index.
When a unique index exists, the Database Engine checks for duplicate values each time data is added by insert operations. Insert operations that would generate duplicate key values are rolled back, and the Database Engine displays an error message. This is true even if the insert operation changes many rows but causes only one duplicate. Partitioned indexes are created and maintained in a similar manner to partitioned tables, but like ordinary indexes, they are handled as separate database objects.
You can have a partitioned index on a table that is not partitioned, and you can have a nonpartitioned index on a table that is partitioned. If you are creating an index on a partitioned table, and do not specify a filegroup on which to place the index, the index is partitioned in the same manner as the underlying table.
This is because indexes, by default, are placed on the same filegroups as their underlying tables, and for a partitioned table in the same partition scheme that uses the same partitioning columns.
When the index uses the same partition scheme and partitioning column as the table, the index is aligned with the table. Creating and rebuilding nonaligned indexes on a table with more than 1, partitions is possible, but is not supported. Doing so may cause degraded performance or excessive memory consumption during these operations.
We recommend using only aligned indexes when the number of partitions exceed 1, When partitioning a non-unique, clustered index, the Database Engine by default adds any partitioning columns to the list of clustered index keys, if not already specified. Indexed views can be created on partitioned tables in the same manner as indexes on tables. In SQL Server, statistics are not created by scanning all the rows in the table when a partitioned index is created or rebuilt.
Instead, the query optimizer uses the default sampling algorithm to generate statistics. A filtered index is an optimized nonclustered index, suited for queries that select a small percentage of rows from a table.
It uses a filter predicate to index a portion of the data in the table. A well-designed filtered index can improve query performance, reduce storage costs, and reduce maintenance costs. The SET options in the Required Value column are required whenever any of the following conditions occur:.
The maximum size for an index key is bytes for a clustered index and 1, bytes for a nonclustered index. Indexes on varchar columns that exceed the byte limit can be created if the existing data in the columns do not exceed the limit at the time the index is created; however, subsequent insert or update actions on the columns that cause the total size to be greater than the limit will fail.
Nonclustered indexes can include non-key columns in the leaf level of the index. These columns are not considered by the Database Engine when calculating the index key size. When tables are partitioned, if the partitioning key columns are not already present in a non-unique clustered index, they are added to the index by the Database Engine. In Object Explorer, click the plus sign to expand the database that contains the table on which you want to create an index with nonkey columns.
Click the plus sign to expand the table on which you want to create an index with nonkey columns. In the New Index dialog box, on the General page, enter the name of the new index in the Index name box. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info.
Contents Exit focus mode. Is this page helpful? Please rate your experience Yes No. Any additional feedback? Note When an index contains all the columns referenced by a query it is typically referred to as covering the query. Besides storing the index key values, the leaf nodes also store row pointers to the data rows that contain the key values. These row pointers are also known as row locators.
If the underlying table is a clustered table, the row pointer is the clustered index key. In case the underlying table is a heap, the row pointer points to the row of the table. We will use the sales. The sales. If you display the estimated execution plan, you will see that the query optimizer scans the clustered index to find the row.
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