We can index across a view containing multiple tables for a start and the where and case clauses can be very sophisticated. This sophistication comes at a price as the index can be larger and is will be updated during an insert whereas a filtered index will only be updated during insert if the new row meets the where clause in the filter. Indexed Views do not support non-unique clustered indexes and the first index on a view have to be clustered because only a clustered index can enforce uniqueness and store the rows at the same time.
What does mean of Filtered Index?A Filtered Index is an optimized non-clustered index which allows us to define a filter predicate with WHERE clause whenever creating the index. A well-designed filtered index can improve query performance, reduce index maintenance costs, and reduce index storage costs compared with full-table indexes.
In very simple words, we can say that “Filtered indexes allow us to create an index on a subset of data using a filtering predicate”.
Type of Indexes in SQL
What does mean of Indexed view?
An Indexed View is the most powerful feature of SQL which was introduced with SQL Server 2000. The main purpose of the indexed view is to run the queries faster and improve the performance of the application. Indexed view has a unique clustered index nature and let us pre-computes all sorts of joins, aggregations, and computations because we can’t use these conditions into every query.
What are differences between Filtered Index and Indexed View?
What are differences between Filtered Index and Indexed View?
Filtered indexes have the following advantages over indexed views-
Criteria
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Filtered Index
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Indexed Views
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Maintenance Costs
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Reduced index maintenance costs because the query processor uses fewer CPU resources to update a filtered index
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The query processor uses more CPU resources to update a Indexed View.
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Plan Quality
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Improved plan quality because during query compilation, the query optimizer considers using a filtered index in more situations
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They are not so benificial in the query optimizer as Filtered Index
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Online index rebuilds
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A Filtered indexes while they are available for queries
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Online index rebuilds are not supported for indexed views
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Non-unique indexes
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Filtered indexes can be non-unique
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Indexed views must be unique
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Only One Table
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A Filtered Index is created on column(s) of a particular table.
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Index Views can be created on column(s) from multiple base tables.
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Simple WHERE criteria
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A Filtered Index can not use complex logic in its WHERE clause, for example the LIKE clause, NOT IN, OR and dynamic / non-deterministic predicates like WHERE col >= DATEADD(DAY, -1, GETDATE()) are not allowed, only simple comparison operators are allowed.
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This limitation does not apply to indexed views and you can design your criteria as complex as you want.
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Type of Indexes in SQL
References:
https://msdn.microsoft.com/en-IN/library/ms191432(v=sql.90).aspx
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