"Summary: In SQL Server 2005, any table can have either clustered indexes or be organized as a heap (without a clustered index.) This white paper summarizes the advantages and disadvantages, the difference in performance characteristics, and other behaviors of tables that are ordered as lists (clustered indexes) or heaps. The performance for six distinct scenarios where DML operations are performed on these tables are measured and detailed observations presented. This white paper provides best practice recommendations on the merits of the two types of table organization, along with examples of when you might want to use one or the other."
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