XML Data in MS SQL Server Query and Modification Steven Blundy, Duc Duong, Abhishek Mukherji, Bartlett Shappee CS561

Outline Introduction XML Data Type  Structure and storage  Schema, validation  Methods Publishing  FORXML Queries

Approaches for XML integration to DB Mid-tier  Bi-directional XML view Query view using XPath Schema-driven approach for shredding Server-side  rowset-to-XML aggregator for XML Publishing - FOR XML  Query-driven shredding mechanism- Open XML

SQL SERVER 2005 XML Architecture

XML Storage - Native Checks Well Formedness  Validation is optional XML Documents or Fragments

XML Storage - DB SQL BLOB  Allows for utilization BLOB optimizations Streaming Parsing Compression  Unicode (UTF-16) Strings - UNTYPED Requires Conversion  XML Schema - TYPED Encode to match schema Much more efficient

XML Storage - The Numbers Advantages of Binary Storage  20 to 30% Size Reduction  Faster Limitations  2gb of stored binary per instance  Hierarchy is limited to 128 Levels

Storage - Schema Storage Optimization  Size  Processing Uses the XML Infoset Defined in an XMLSchemaCollection

Validation - Schema XML Schema Collection  Stores 1+ XML Schemas Identified by Name Space Not the Same as Constraints (No Business Logic)  Metadata Entity  Certain Type are Format Constrained i.e. Date must use ISO 8601 format Uses the XML Infoset

Validation - Schema Collection CREATE XML SCHEMA COLLECTION myCollection AS '<xsd:schema xmlns:xsd=" xmlns=" elementFormDefault="qualified" targetNamespace=" '

Validation - How? At Data Entry  Validness checked when typed data is inserted Checking Data  Applied using Cast Updated Schema  Does not Require re-validation

XML DT Methods All evaluate an XQuery Methods  query() - returns XML output  exists() - checks if expression results in nodes  nodes() - returns XML DT values  value() - returns value as SQL DT  modify() - modify XML data

query() & nodes() methods Both take XQuery string query() returns list of untyped XML nodes  Can be converted to strings  For SELECT output nodes() returns list of typed XML nodes  All XML DT methods available  count(*) works  No converting to strings

exist() & value() methods exist()  returns true if XQuery returns any nodes value()  Takes 2 params: an XQuery & a SQL DT  Converts xml value returned by XQuery to specified SQL type

Example: value() SELECT data.value(‘(/bibliograph/book/[1]/title)[1]’, ‘NVARCHAR(255)’) AS Title FROM Test Title Design Patterns

Example: value() w/ nodes() SELECT book.value(‘(title)[1]’, ‘NVARCHAR(255)’) AS Title FROM Test CROSS APPLY data.nodes(‘/bibliograph/book’) AS R(book) Title Design Patterns All about XML …

Example: exist() SELECT book.value(‘(title)[1]’, ‘NVARCHAR(255)’) AS Title FROM Test CROSS APPLY data.nodes(‘/bibliograph/book’) AS R(book) WHERE data.exist(‘/bibliograph/book’) = 1 Title Design Patterns All about XML …

modify() method Uses extended XQuery  insert, delete, and replace keywords Used in SQL UPDATEs

Example: modify() UPDATE docs SET xCol.modify(‘ insert Background after

Example 2: modify() UPDATE XmlCatalog SET Document.modify (' declare namespace bk = " replace value of (/bk:bookstore/bk:book 0"]/bk:price)[1] with 49.99')

XML Publishing select CustomerID as City as "address/city", PostalCode as "address/zip", ContactName as "contact/name", Phone as "contact/phone", from Customers for xml path('Customer'), root('Doc')

Additional Papers Used XML Support in Microsoft SQL Server 2005  Shankar Pal, Mark Fussell, and Irwin Dolobowsk  XML Best Practices for Microsoft SQL Server 2005  Shankar Pal, Vishesh Parikh, Vasili Zolotov, Leo Giakoumakis, Michael Rys  us/library/ms345115(d=printer).aspx us/library/ms345115(d=printer).aspx

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