SPal's WebLog : SQL Server

SQL Script for Typed XML used in MSDN Webcast on Dec 7, 2004

SPal — Wed, 22 Dec 2004 05:26:00 GMT

Hello!

This posting contains T-SQL script for working with typed (i.e. XML schema bound) XML. I used it during the MSDN webcast on Tue, Dec 7, 2004, on “Introducing XML in SQL Server 2005”. Yesterday’s posting (http://weblogs.asp.net/spal/archive/2004/12/20/327635.aspx) contained the script for untyped XML. Thanks for your patience!

I have added some more annotation to the script to make it more readable – so please don’t skip the comments. I have the habit of repeating key phrases – this makes the text a little verbose but avoids ambiguity.

Here is a list of the MSDN whitepapers on XML support in SQL Server 2005 that you might find useful:

XML feature overview: http://msdn.microsoft.com/xml/default.aspx?pull=/library/en-us/dnsql90/html/sql2k5xml.asp
XML Best Practices (I refer to it in the script below): http://msdn.microsoft.com/xml/default.aspx?pull=/library/en-us/dnsql90/html/sql25xmlbp.asp
XML Optimizations: http://msdn.microsoft.com/xml/default.aspx?pull=/library/en-us/dnsql90/html/sqloptxml.asp
XML Generation from tables: http://msdn.microsoft.com/xml/buildingxml/xmlanddatabase/default.aspx?pull=/library/en-us/dnsql90/html/forxml2k5.asp

Of course, SQL Server 2005 books-online is an invaluable resource.

I hope these scripts help you get started with the new XML features.

Thanks and enjoy!

Shankar

Program Manager

Microsoft SQL Server

-----------------------------------------------------------------------

-- First, the formality:

-- Use of included script samples are subject to the terms specified at

-- http://www.microsoft.com/info/cpyright.htm

-----------------------------------------------------------------------

-- This T-SQL script illustrates the use of typed (i.e. XML schema-bound) XML data type on SQL Server 2005.

---------------------------------------------------------------------------------------------------------

-- NOTE: Before we get started, save the following data literally into a file C:\temp\TypedPropTable.txt.

-- If you choose a different path or file name, remember to change the file path in the script below. The

-- script uses this file to illustrate bcp’ing data into an XML column

---------------------------------------------------------------------------------------------------------

12 <p:book xmlns:p="http://www.microsoft.com/book" subject="drama" releasedate="2002" ISBN="0-1234-1588-2"><title>Battle of Troy</title><author><first-name>Matthew</first-name><last-name>Robson</last-name></author><price>19.99</price></p:book> 0

24 <q:dvd xmlns:q="http://www.microsoft.com/DVD" subject="drama" releasedate="1977"><title>The Godfather</title><price>12.99</price></q:dvd> 0

----------------------------------------

--- We are good to go now.

--- We’ll start with a clean database

----------------------------------------

USE master

if EXISTS (SELECT * FROM sys.databases

WHERE name = 'TypedProperty')

DROP DATABASE TypedProperty

CREATE DATABASE TypedProperty

USE TypedProperty

----------------------------------------------------------

--- Create an XML schema collection containing BOOK schema

----------------------------------------------------------

CREATE XML SCHEMA COLLECTION myCollection

'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns="http://www.microsoft.com/book"

targetNamespace="http://www.microsoft.com/book">

<xsd:element name="book" type="bookType" />

<xsd:complexType name="bookType">

<xsd:sequence>

<xsd:element name="title" type="xsd:string" />

<xsd:element name="author" type="authorName" maxOccurs="unbounded"/>

<xsd:element name="price" type="xsd:decimal" />

</xsd:sequence>

<xsd:attribute name="subject" type="xsd:string" />

<xsd:attribute name="releasedate" type="xsd:integer" />

<xsd:attribute name="ISBN" type="xsd:string" />

</xsd:complexType>

<xsd:complexType name="authorName">

<xsd:sequence>

<xsd:element name="first-name" type="xsd:string" />

<xsd:element name="last-name" type="xsd:string" />

</xsd:sequence>

</xsd:complexType>

</xsd:schema>'

-------------------------------------------------------------

--- Create a table containing a typed XML column

--- NOTE: the typed XML column as declared below

--- allows XML “content” to be stored therein (i.e.

--- multiple top-level elements. This is the default.

--- You can restrict it to one top-level element by declaring

--- the XML column as XML (DOCUMENT dbo.myCollection)

-------------------------------------------------------------

CREATE TABLE PropTable (

assetID INT PRIMARY KEY,

xProp XML (dbo.myCollection))

----------------------------------------------------------

--- Alter the XML schema collection by adding the XML

--- schema for DVD. Altering an XML schema collection is

--- allowed even after the XML column has been populated

----------------------------------------------------------

ALTER XML SCHEMA COLLECTION myCollection

ADD

'<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns="http://www.microsoft.com/DVD"

targetNamespace="http://www.microsoft.com/DVD">

<xsd:element name="dvd" type="dvdType" />

<xsd:complexType name="dvdType">

<xsd:sequence>

<xsd:element name="title" type="xsd:string" />

<xsd:element name="price" type="xsd:decimal" />

</xsd:sequence>

<xsd:attribute name="subject" type="xsd:string" />

<xsd:attribute name="releasedate" type="xsd:integer" />

</xsd:complexType>

</xsd:schema>'

----------------------------------------------------------

--- Insertion of data into the typed XML column

--- The XML schema namespace specified in the XML instance

--- identifies the XML schema in the XML schema collection

--- to validate against. If the data does not validate

--- against the schema, it will be rejected with appropriate

--- error message

----------------------------------------------------------

--- Insert a literal value for XML

INSERT INTO PropTable VALUES (1,

'<p:book xmlns:p="http://www.microsoft.com/book"

subject="security" releasedate="2002" ISBN="0-7356-1588-2">

<title>Writing Secure Code</title>

<first-name>Michael</first-name>

<last-name>Howard</last-name>

</author>

<first-name>David</first-name>

<last-name>LeBlanc</last-name>

</author>

</p:book>')

-------------------------------------------------------------------------------------------------

--- Promote price property into a separate column.

--- The <price> value will also be retained in XML instances.

--- The query processor will maintain the consistency between the two columns.

--- Property promotion is useful when a significant percentage of the queries are based on price.

---

--- For promoting multi-valued properties, you need to create a “property table” and maintain it

--- using triggers. This is discussed in the XML Best Practices whitepaper on MSDN (link above)

-------------------------------------------------------------------------------------------------

--- Create user-defined function for Price. This computes

--- the price of the asset irrespective of its asset class.

--- You can promote properties per asset type by specifying

--- the appropriate XML schema namespace in the query below

CREATE FUNCTION udf_get_price (@xData xml(dbo.myCollection))

RETURNS real

WITH SCHEMABINDING

BEGIN

RETURN (SELECT @xData.value ('(//price)[1]', 'real'))

END

----- Add a computed column to the table for Price

----- Computed columns are read-only

ALTER TABLE PropTable

ADD Price AS dbo.udf_get_price(xProp) PERSISTED

----- Check the contents of the table: one row with the price

----- value promoted into Price column

SELECT * FROM PropTable

--- Index the computed column

CREATE NONCLUSTERED INDEX idx_Price ON PropTable (Price)

---------------------------------------------------------------

--- Create Primary XML index – this can be created before the

--- non-clustered index on Price

--- XML index is a new type of index because it retains the

--- structure of the XML instance (e.g. document order,

--- parent-child hierarchy) in addition to values within

--- the XML instance. It is internally implemented as a B+ tree

---------------------------------------------------------------

CREATE PRIMARY XML INDEX idx_xProp ON PropTable(xProp)

-------------------------------------------------------------------------------------

--- Create 'PATH' Secondary XML index

--- This helps with path-based queries, which are predominat in practice

--- Secondary XML indexes can be created after the primary XML index on an XML column

--- Other types of secondary XML indexes – VALUE and PROPERTY

--- See the MSDN whitepapers for more description and usage guidance of these indexes

-------------------------------------------------------------------------------------

CREATE XML INDEX idx_xProp_PATH ON PropTable(xProp)

USING XML INDEX idx_xProp

FOR PATH

----------------------------------------------------

--- Loading XML from file using bcp

--- This uses the data file that was created upfront

----------------------------------------------------

--- Load 2 more rows into the table

EXEC master.dbo.xp_cmdshell

'bcp TypedProperty.dbo.PropTable in C:\temp\TypedPropTable.txt -c -q -T'

--- Check contents of table: 3 rows with the price value promoted

SELECT * FROM PropTable

--------------------------

--- QUERYING XML DATA TYPE

--------------------------

--- Find assets that are priced between $9.99 and $29.99

SELECT assetID, xProp, Price

FROM PropTable

WHERE xProp.exist ('//price[. > 9.99 and . < 29.99]') = 1

-- Wait a minute! The price value has been promoted, so let’s use that!!

-- The query plan is simpler using the promoted column since the value is

-- pre-computed. Also, the non-clustered index on the promoted column helps performance

SELECT assetID, xProp, Price

FROM PropTable

WHERE Price > 9.99 AND Price < 29.99

--- What if you want to restrict the search to a specific asset type?

--- The Price column is oblivious of the asset type

--- Let’s try: Find books (not DVDs) priced between $9.99 and $29.9

--- The query needs to specify the XML schema namespace for "book" and

--- query the XML column

SELECT assetID, xProp, Price

FROM PropTable

WHERE xProp.exist ('

declare namespace p= "http://www.microsoft.com/book"

/p:book/price[. > 9.99 and . < 29.99]') = 1

--- Let’s try grouping based on values within the XML column, such as

--- the number of assets per release year

--- You have to retrieve the release year in a sub-query for grouping

SELECT Year, count(AssetID) Asset_Count

FROM (

SELECT xProp.value ('(//@releasedate)[1]', 'int'), assetID

FROM PropTable

) R(Year, AssetID)

GROUP BY Year

------------------------------

--- XML DATA TYPE MODIFICATION

------------------------------

--- Lower an asset's price by 10% - it's holiday season and some discount is appreciated!

UPDATE PropTable

SET xProp.modify ('

replace value of (//price)[1]

with 0.9*(//price)[1]

--- Verify update

--- Notice that the Price column is kept in sync with the

--- value in the XML column – you didn’t need to maintain it!

SELECT *

FROM PropTable

--- Delete an author of a book given the book's ISBN

--- and the author's name.

--- This doesn’t happen often in practice but is good enough

--- to illustrate the idea

UPDATE PropTable

SET xProp.modify(

'declare namespace p= "http://www.microsoft.com/book"

delete /p:book[@ISBN = "0-7356-1588-2"]/author[first-name = "David"]')

--- Add an author (new subtree) to a book given its ISBN

--- Notice that the point of insertion is specified using "before"

--- Besides “before”, other possibilites are “after” and “into”

UPDATE PropTable

SET xProp.modify(

'declare namespace p= "http://www.microsoft.com/book"

insert <author>

<first-name>David</first-name>

<last-name>LeBlanc</last-name>

</author>

before (/p:book[@ISBN = "0-7356-1588-2"]/author)[1]')

WHERE xProp.exist ('

declare namespace p= "http://www.microsoft.com/book"

/p:book[@ISBN = "0-7356-1588-2"]') = 1

This posting is provided "AS IS" with no warranties, and confers no rights.

SQL Script used in MSDN Webcast on Dec 7, 2004

SPal — Tue, 21 Dec 2004 02:30:00 GMT

I made an MSDN webcast on Tue, Dec 7, 2004, on “Introducing XML in SQL Server 2005”. I showed a couple of T-SQL scripts that many of you found useful. This posting contains the demo script for working with untyped XML data. My apologies for the delay in posting!

I’ll follow this up over the next few days with postings of the script for typed (i.e. XML schema bound) XML data and the Q&A for the webcast.

The MSDN whitepaper at http://msdn.microsoft.com/xml/default.aspx?pull=/library/en-us/dnsql90/html/sql2k5xml.asp contains many code snippets with more explanations. You may find it useful as well.

Thanks and enjoy!

Shankar

Program Manager

Microsoft SQL Server

-----------------------------------------------------

-- First, a little formality: Use of included script

-- samples are subject to the terms specified at

-- http://www.microsoft.com/info/cpyright.htm

-----------------------------------------------------

-- This T-SQL script illustrates the use of untyped

-- (i.e. not XML schema-bound) XML data type on SQL

-- Server 2005.

-----------------------------------------------------

-- NOTE: Before we get started, save the following

-- XML content into a file C:\temp\xmlfile.xml. If

-- you choose a different path or file name, remember

-- to change the file path in the script below.

<title>XML Schema</title>

</chapter>

<title>Benefits</title>

</chapter>

<title>Features</title>

</chapter>

</book>

---------------------------

--- Off we go - Cleanup

---------------------------

USE master

if EXISTS (SELECT * FROM sys.databases WHERE name = 'TSqlDemo')

DROP DATABASE TSqlDemo

------------------------------------------

--- Initialization - create a new database

------------------------------------------

CREATE DATABASE TSqlDemo

USE TSqlDemo

----------------------------------------------

--- Create table containing untyped XML column

----------------------------------------------

CREATE TABLE docs (

id INT PRIMARY KEY,

xbook XML)

-------------------------------

--- Insertion of data

-------------------------------

--- Insert a literal value for XML

INSERT INTO docs VALUES (1,

'<book ISBN="0-7356-1588-2">

<title>Background</title>

</chapter>

<title>Epilogue</title>

</chapter>

</book>')

---------------------------

--- Loading XML from file

---------------------------

--- Add a row to the table

INSERT INTO docs

SELECT 2, xbook

FROM (SELECT *

FROM OPENROWSET (BULK 'C:\temp\xmlfile.xml',SINGLE_BLOB)

AS xbook) AS R(xbook)

--- Check content of table – there are two rows

SELECT * FROM docs

--------------------------

--- QUERYING XML DATA TYPE

--------------------------

--- Find chapter title of chapter number 3 and later

--- Illustrates the use of query() method

--- Notice how a new element <topic> is constructed from the persistent

--- data

SELECT id, xbook.query('

for $c in

/book[@ISBN = "0-7356-1588-2"]//chapter

where $c/@num >= 3

return <topic>{data($c/title)}</topic>

FROM docs

--- Eliminate empty XML result using exist() method

SELECT id, xbook.query('

for $c in

/book[@ISBN = ''0-7356-1588-2'']//chapter

where $c/@num >= 3

return <topic>{data($c/title)}</topic>

FROM docs

WHERE xbook.exist ('/book[@ISBN = ''0-7356-1588-2'']') = 1

--- Extract scalar value (title of Chapter 3)

--- Uses value() method

SELECT id, xbook.value(

'data((/book//chapter[@num = 3]/title)[1])',

'nvarchar(1024)') AS Title

FROM docs

--- List all chapter titles

--- Notice how the nodes() method explodes an XML instance into a

--- rowset of XML nodes matching an XQuery expression

SELECT id, nref.query('.') AS Chapter,

nref.value('.', 'nvarchar(1024)') AS Title

FROM docs

CROSS APPLY xbook.nodes ('/book//chapter') AS R(nref)

WHERE nref.exist('.[@num >= 2]')=1

----------------------------------------

--- Cross domain query:

--- Query across relational and XML data

----------------------------------------

--- Using value from a T-SQL variable

DECLARE @num int

SET @num = 1

SELECT id,

@num AS ChapterNum,

xbook.query(

'for $s in /book//chapter[@num=sql:variable("@num")]

return <topic>{data($s/title)}</topic>')

FROM docs

------------------------------

--- XML DATA TYPE MODIFICATION

------------------------------

--- Change title of chapter 3 to "Algorithms"

UPDATE docs

SET xbook.modify (

'replace value of

(/book[@ISBN = "0-7356-1588-2"]//chapter[@num=1]/title/text())[1]

with "Algorithms"')

--- Verify update

SELECT id, xbook

FROM docs

--- Insert new subtree (chapter)

UPDATE docs

SET xbook.modify(

'insert <chapter num="2">

<title>Introduction</title>

</chapter>

after (/book//chapter[@num=1])[1]')

--- Verify insertion

SELECT xbook

FROM docs

--- Delete chapter #1

UPDATE docs

SET xbook.modify(

'delete /book//chapter[@num=1]')

--- Verify deletion

SELECT xbook

FROM docs

This posting is provided "AS IS" with no warranties, and confers no rights.