SQL Server Developer Center: XML Indexes in SQL Server 2005

SQL Server Developer Center: XML Indexes in SQL Server 2005: "Although not everyone would agree, one of the main reasons for the success of the relational database has been the inclusion of the SQL language. SQL is a set-based declarative language. As opposed to COBOL (or most .NET-based languages for that matter), when you use SQL, you tell the database what data you are looking for, rather than how to obtain that data. The SQL query processor determines the best plan to get the data you want and then retrieves the data for you. As query-processing engines mature, your SQL code will run faster and better (less I/O and CPU) without the developer making changes to the code. What development manager wouldn't be pleased to hear that programs will run faster and more efficiently with no changes to source code because the query engine gets better over time?
One of the ways to allow the query processor the choice of optimized access is to create indexes over the data. Creating the correct index can dramatically change how the query engine evaluates the query. You decide which indexes to create by analyzing which queries you actually perform and figuring up how the engine could optimize those queries. A tool to analyze query workloads and suggest indexes comes with SQL Server. In SQL Server 2005, this tool is Database Tuning Advisor. "