Module 17

Storing XML Data in SQL Server® 2008 R2

Module Overview

• Introduction to XML and XML Schemas

• Storing XML Data and Schemas in SQL Server

• Implementing the XML Data Type

Lesson 1: Introduction to XML and XML Schemas

• Discussion: XML Usage in SQL Server

• Core XML Concepts

• Fragments vs. Documents

• XML Namespaces

• XML Schemas

• Appropriate Usage of XML Data Storage in SQL Server

• Demonstration 1A: Introduction to XML and XML Schemas

Discussion: XML Usage in SQL Server

• Traditionally, database administrators have not worked with XML

• Database developers often want to store XML data in SQL Server

• Many aspects and components of SQL Server are now XML-based, including those often only used by administrators XML data type and schema collections

DDL triggers

Extended events

Logon triggers

Event notifications

Service Broker

Core XML Concepts

• Is a plain-text, Unicode-based meta-language

• Represents both structured and semi-structured data

• Is not tied to any programming language, OS, or vendor

<?xml version="1.0" encoding="iso-8859-1" ?><?xml-stylesheet href="orders.xsl"?>

<order id="ord123456"> <customer id="cust0921"> <first-name>Dare</first-name> <last-name>Obasanjo</last-name> <address> <street>One Microsoft Way</street> <city>Redmond</city> <state>WA</state> <zip>98052</zip> </address> </customer></order>

<?xml version="1.0" encoding="iso-8859-1" ?><?xml-stylesheet href="orders.xsl"?>

<order id="ord123456"> <customer id="cust0921"> <first-name>Dare</first-name> <last-name>Obasanjo</last-name> <address> <street>One Microsoft Way</street> <city>Redmond</city> <state>WA</state> <zip>98052</zip> </address> </customer></order>

AttributeAttribute

ElementElement

Processing InstructionProcessing Instruction

Fragments vs. Documents

• Well-formed XML has only one top-level element

• Documents with multiple top-level elements are fragments

<order id="ord123456"> <customer id="cust0921" /></order><order id="ord123457"> <customer id="cust0925" /></order>

<order id="ord123456"> <customer id="cust0921" /></order><order id="ord123457"> <customer id="cust0925" /></order>

<?xml version="1.0" encoding="iso-8859-1" ?><orders> <order id="ord123456"> <customer id="cust0921" /> </order> <order id="ord123457"> <customer id="cust0925" /> </order></orders>

<?xml version="1.0" encoding="iso-8859-1" ?><orders> <order id="ord123456"> <customer id="cust0921" /> </order> <order id="ord123457"> <customer id="cust0925" /> </order></orders>

DOCUMENT

FRAGMENT

XML Namespaces

<Customer xmlns="urn:AW_NS" xmlns:o="urn:AW_OrderNS" CustomerID="1" CustomerType="S"> <o:Order SalesOrderID="43860" Status="5" OrderDate="2001-08-01T00:00:00"> <o:OrderDetail ProductID="761" Quantity="2"/> <o:OrderDetail ProductID="770" Quantity="1"/> </o:Order></Customer>

<Customer xmlns="urn:AW_NS" xmlns:o="urn:AW_OrderNS" CustomerID="1" CustomerType="S"> <o:Order SalesOrderID="43860" Status="5" OrderDate="2001-08-01T00:00:00"> <o:OrderDetail ProductID="761" Quantity="2"/> <o:OrderDetail ProductID="770" Quantity="1"/> </o:Order></Customer>

• XML namespace is a collection of names that can be usedas element or attribute names

• It is used to avoid conflicts with other names

• Prefix typically assigned to reference the namespace

XML Schemas

• XML schema describes the structure of XML document

• XML schema language is also called XML Schema Definition (XSD)

• Validation constraintsSQL Server validates the instance

• Data type informationSchemas provide info about types of attributes and elements

An XML schema provides the following:

Appropriate Usage of XML Data Storage in SQL Server

Reasons to store XML data in SQL Server

You wish to share, query, and modify XML in an efficient and transacted way

You have both relational and XML data and need to have interoperability

You need to build cross-domain applications and need portability of data

Your data is sparse or you do not know the structure of your data

Order matters within your data

You want the server to guarantee the XML is well-formed and optionally validate your data against a schema

You want to index your XML data

Demonstration 1A: Introduction to XML and XML Schemas

In this demonstration, you will see how:

• XML is structured

• Documents differ from fragments

• XML schemas are structured

Lesson 2: Storing XML Data and Schemas in SQL Server

• XML Data Type

• XML Schema Collections

• Untyped vs. Typed XML

• CONTENT vs. DOCUMENT

• Demonstration 2A: Typed vs. Untyped XML

XML Data Type

-- usage within table definitionCREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml);-- usage as local variableDECLARE @Settings xml;-- usage as parameter to stored procedureCREATE PROCEDURE App.SaveSettings(@SettingsToSave xml) AS ...

-- usage within table definitionCREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml);-- usage as local variableDECLARE @Settings xml;-- usage as parameter to stored procedureCREATE PROCEDURE App.SaveSettings(@SettingsToSave xml) AS ...

• Is a native data type for XML

• Lets you store XML documents and fragments

• Is used for columns, variables, or parameters

• Exposes methods to query and modify XML

XML Schema Collections

The XML schema collection:

• Validates XML instances

• Types the XML data as it is stored in the database

• SQL Server provides native storage of XML data with the xml data type

• You can optionally associate XSD schemas with an xml data type through an XML schema collection

• Stores the imported XML schemas

Untyped vs. Typed XML

• Use untyped XML data type in the following situations:

• You do not have a schema for your XML data

• You have schemas, but don’t want server to validate data (there is significant impact on a server performing validation)

• Use typed XML data type in the following situations:

• You have schemas and want server to validate XML data

• You want to take advantage of storage and query optimizations based on type information

• You want to take advantage of type information during compilation of your queries

CONTENT vs. DOCUMENT

• XML data type stores CONTENT (including fragments) by default

• Can be required to store DOCUMENT

CREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml (CONTENT App.SettingsSchemaCollection));

CREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml (CONTENT App.SettingsSchemaCollection));

CREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml (DOCUMENT App.SettingsSchemaCollection));

CREATE TABLE App.Settings( SessionID int PRIMARY KEY, WindowSettings xml (DOCUMENT App.SettingsSchemaCollection));

CONTENT

(allows fragments)

DOCUMENT

(no fragments)

Demonstration 2A: Typed vs. Untyped XML

In this demonstration, you will see how to:

• Create an XML SCHEMA COLLECTION

• Use typed XML in a column of a table

• Differentiate between CONTENT and DOCUMENT

Lesson 3: Implementing XML Indexes

• What are XML Indexes?

• Types of XML Indexes

• Demonstration 3A: Implementing XML Indexes

What are XML Indexes?

• XML data can be slow to access

• XML indexes can help with query performance

• Indexes contain details of Nodes Values Paths

Types of XML Indexes

Primary XML Index

Provides a persisted object tree in an internal format that is used to speed access to elements and attributes within the XML

Requires a clustered primary key on the table

Secondary XML Index

Can only be constructed once a primary XML index has been created

Three types of secondary indexes can be constructed to help answer specific XQuery queries rapidly:PATH, PROPERTY, VALUE

Demonstration 3A: Implementing XML Indexes

In this demonstration, you will see how to:

• Create a primary XML index

• Create a secondary XML index

• Query the sys.xml_indexes system view

• Identify the requirement of a clustered primary key on the table by XML indexes

Lab 17: Storing XML Data in SQL Server

• Exercise 1: Appropriate Usage of XML Data Storage in SQL Server

• Exercise 2: Investigate the Storage of XML Data in Variables

• Exercise 3: Investigate the use of XML Schema Collections

• Challenge Exercise 4: Investigate the Creation of Database Columns Based on XML (Only if time permits)

Logon information

Estimated time: 45 minutes

Virtual machine 623XB-MIA-SQL

User name AdventureWorks\Administrator

Password Pa$$w0rd

Lab Scenario

A new developer in your organization has discovered that SQL Server can store XML directly. He is keen to use this mechanism extensively. In this lab, you will decide on appropriate usage of XML within the documented application.

You also have an upcoming project that will require the use of XML data within SQL Server. No members of your current team have experience working with XML data in SQL Server. You need to learn how to process XML data within SQL Server and you have been provided with some sample queries to assist with this learning.

Lab Review

• What is the purpose of an XML schema?

• When would you use untyped XML?

• When would you use typed XML?

Module Review and Takeaways

• Review Questions

• Best Practices