http://www.sql-server-performance.com/2007/optimizing-indexes-general/ SQL Server Performance Tuning Fri, 17 May 2013 13:31:24 +0000 hourly 1 http://wordpress.org/?v=3.5.1 http://www.sql-server-performance.com/2007/optimizing-indexes-general/#comment-362 Christoph D Thu, 09 Jun 2011 12:16:45 +0000 http://www.sql-server-performance.com/?=207#comment-362 Queries that include either the DISTINCT or the GROUP BY clauses can be optimized by including appropriate indexes. Any of the following indexing strategies can be used:
•Include a clustered index on the columns found in the SELECT clause.
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This may be correct for nonclustered indexes to be sure that it is a covering index but the leaf-level of a clustered data is always the data of the table itself.
I would highly suggest to put a clustered index, as it was said before, on an increasing unique value if there are many data manipulations on this table or on a column that is queried for a specific range very often (like a date maybe) if there are many selects on this range to improve performance for these queries.

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