问题
I was told that there is new a feature in SQL Server 2005 called index filters.
What I want to do is add an Index to a column and have the index ignore null values.
I can't find good information on this feature (maybe my source is wrong). Can anyone provide additional information on this feature?
回答1:
CREATE INDEX ix_mytable_mycolumn ON mytable(mycolumn) WHERE mycolumn IS NOT NULL
This will work only in SQL Server 2008, though.
From the docs:
WHERE <filter_predicate>Creates a filtered index by specifying which rows to include in the index. The filtered index must be a nonclustered index on a table. Creates filtered statistics for the data rows in the filtered index.
回答2:
I think you are speaking about filtered indexes, which were introduced in SQL Server 2008, not 2005.
For information, have a look at this article: http://www.sql-server-performance.com/articles/dba/Filtered_Indexes_in_SQL_Server_2008_p1.aspx
Or just do a google search for "sql server filtered indexes".
来源：https://stackoverflow.com/questions/1560342/sql-server-2005-index-filter-feature