It’s not hard to imagine that the SQL Server team discovered early on that the standard SQL Server relational b-tree indexing mechanisms wouldn’t work with XML data. The XQuery language, which I discussed in Chapter 5, is designed to query XML nodes while SQL is designed to query relational data stored in tables. XQuery supports a wide variety of functions, operators, and predicates that require access to all types of nodes, especially element and attribute nodes. The standard SQL Server relational indexes do not optimize access to individual XML nodes, which is a requirement to optimize XQuery access.
KeywordsQuery Plan Query Engine Database Engine Index Creation Secondary Index
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