SPal's WebLog

MSDN presentation on "Introducing XML in SQL Server 2005"

SPal — Wed, 09 Nov 2005 11:06:00 GMT

First of all, I'd like to thank all those who took the time to attend my presentation today (Nov 8, 2005). I hope you found it useful. The launch of SQL Server 2005, Visual Studio 2005 and BizTalk Server 2006 is a matter of great pride and honor for us all.

The website with links to the XML schemas published by SQL Server is http://schemas.microsoft.com/sqlserver. Look at the one called SqlTypes for the XML schema types corresponding to the built-in SQL types. This was one of the questions during the presentation.

The Transact-SQL script I presented is below. I hope you get a chance to run it! Play with it to discover the power of the native XML support. For more information about the XML support, check out the REFERENCES in the left pane.

Enjoy! Let me know if you have questions or would like me to address any issues in the blog.

Shankar

Program Manager

Microsoft SQL Server

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

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.

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

--- Cleanup

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

USE master

--- Drop the existing database

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

DROP DATABASE MSDN

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

--- Initialization

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

--- Create a new database called MSDN

CREATE DATABASE MSDN;

USE MSDN;

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

---- Drop the meeting notes XML schema collection

IF EXISTS (select name from sys.xml_schema_collections where name='meetingNotesCollection')

DROP XML SCHEMA COLLECTION meetingNotesCollection;

CREATE XML SCHEMA COLLECTION meetingNotesCollection

'<xsd:schema

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

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

targetNamespace="http://www.microsoft.com/meetingNotes"

elementFormDefault="qualified">

<xsd:element name="meetingNotes" type="meetingNotesType"/>

<xsd:complexType name="meetingNotesType" mixed="true">

<xsd:sequence>

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

<xsd:element name="meetingDate" type="xsd:date"/>

<xsd:element name="participants"

type="participantType" />

<xsd:element name="notes" type="noteType" />

<xsd:element name="actionItem" type="actionItemType"/>

</xsd:sequence>

</xsd:complexType>

<xsd:complexType name="participantType" mixed="true">

<xsd:sequence>

<xsd:element name="participant" type="xsd:string"

minOccurs="1" maxOccurs="unbounded" />

</xsd:sequence>

</xsd:complexType>

<xsd:complexType name="noteType" mixed="true">

<xsd:sequence>

<xsd:element name="note" type="xsd:string"

minOccurs="0" maxOccurs="unbounded"/>

</xsd:sequence>

</xsd:complexType>

<xsd:complexType name="actionItemType" mixed="true">

<xsd:sequence>

<xsd:element name="description" type="xsd:string"

minOccurs="0" maxOccurs="unbounded"/>

</xsd:sequence>

</xsd:complexType>

</xsd:schema>';

--- Create a table to store MeetingNotes

CREATE TABLE meetingData (

id int PRIMARY KEY,

meetingNotes XML (meetingNotesCollection))

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

--- Insertion of data

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

--- Insert a literal value for XML

INSERT INTO meetingData VALUES (1,

'<p:meetingNotes

xmlns:p="http://www.microsoft.com/meetingNotes">

<p:title>Discussion of XML presentation</p:title>

<p:meetingDate>2005-10-03Z</p:meetingDate>

<p:participants>

<p:participant>Shankar</p:participant>

<p:participant>Brandon</p:participant>

</p:participants>

<p:notes>

<p:note>Equal amount of slides and demos</p:note>

<p:note>VS-focused slides</p:note>

<p:note>SQL/CLR project for XML processing</p:note>

</p:notes>

<p:actionItem>

<p:description>Work on slides - Shankar</p:description>

<p:description>Work on demos - Shankar</p:description>

</p:actionItem>

</p:meetingNotes>');

--- Insert more data into the table

INSERT INTO meetingData VALUES (2,

'<meetingNotes xmlns="http://www.microsoft.com/meetingNotes"><title>Discussion of CDP and Office11</title><meetingDate>2005-09-29Z</meetingDate><participants><participant>Anilnori</participant><participant>Soumitras</participant> <participant>shankarp</participant></participants><notes><note>Format of Word document and storage</note></notes><actionItem><description>Need to put all ideas into a document</description></actionItem></meetingNotes>');

INSERT INTO meetingData VALUES (3,

'<meetingNotes xmlns="http://www.microsoft.com/meetingNotes"><title>Discussion of TechReady presentation</title><meetingDate>2005-08-02Z</meetingDate><participants><participant>shankarp</participant><participant>heraino</participant></participants><notes> <note>Outline the features</note><note>Show architecture diagram</note></notes><actionItem><description>Update the presentation - shankarp</description></actionItem></meetingNotes>');

--- Table contents

SELECT * FROM meetingData;

--- Index the XML column in the table

CREATE PRIMARY XML INDEX idx_xml ON meetingData(meetingNotes);

---- Create PATH secondary XML index

CREATE XML INDEX idx_xml_PATH

ON meetingData(meetingNotes)

USING XML INDEX idx_xml

FOR PATH;

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

--- QUERYING XML DATA TYPE

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

--- Find the action items

SELECT meetingNotes.query ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

/meetingNotes/actionItem/description')

FROM meetingData;

--- Find the action items, one per row

--- With on-the-fly element construction

SELECT dref.query ('<workitem>{data(.)}</workitem>')

FROM meetingData CROSS APPLY

meetingNotes.nodes ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

/meetingNotes/actionItem/description') R(dref);

--- Find the action items, one per row

--- With no element tags

SELECT dref.value ('.', 'nvarchar(256)')

FROM meetingData CROSS APPLY

meetingNotes.nodes ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

/meetingNotes/actionItem/description') R(dref);

--- Find meetings with at least 3 participants

SELECT *

FROM meetingData

WHERE meetingNotes.exist ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

/meetingNotes[count (//participant) > 2]') = 1;

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

--- Promote meeting #participants property

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

--- Create user-defined function for #participants

CREATE FUNCTION udf_get_pCount (

@xData xml(dbo.meetingNotesCollection))

RETURNS int

WITH SCHEMABINDING

BEGIN

RETURN (

SELECT @xData.value ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

count(//participant)', 'int'))

END

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

ALTER TABLE meetingData

ADD PCount AS dbo.udf_get_pCount(meetingNotes);

----- Check content of table

SELECT * FROM meetingData;

--- Index the computed column

CREATE NONCLUSTERED INDEX idx_pCount

ON meetingData(pCount);

-- Simpler alternative to the previous XQuery:

SELECT *

FROM meetingData

WHERE PCount > 2;

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

--- XML DATA TYPE MODIFICATION

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

--- Add a new participant to a meeting

UPDATE meetingData

SET meetingNotes.modify ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

insert <participant>Jinghao</participant>

into (/meetingNotes/participants)[1]')

WHERE id = 1;

--- Verify update

SELECT * FROM meetingData;

--- Modify the title of a meeting

UPDATE meetingData

SET meetingNotes.modify ('

declare default element namespace "http://www.microsoft.com/meetingNotes";

replace value of (/meetingNotes/title)[1]

with "Discussion of XML presentation for MSDN"')

WHERE id = 1;

--- Verify update

SELECT * FROM meetingData

XQuery implementation in SQL Server 2005

SPal — Wed, 21 Sep 2005 05:02:00 GMT

I made at presentation on September 1st on our XQuery implementation at the International Conference on Very Large Databases at Trondheim, Norway. The paper contains a lot of useful information, which, I hope, you will enjoy. The link is: http://www.vldb2005.org/program/paper/thu/p1175-pal.pdf.

I'm adding this link to the left pane as well for future reference.

I hope you like the content.

Thank you,

Shankar

Rebuild XML indexes when upgrading from Beta 2 to June CTP of SQL Server 2005

SPal — Wed, 29 Jun 2005 01:21:00 GMT

Setup upgrade to June CTP of SQL Server 2005 is unavailable. Typically, you would uninstall the existing build of SQL Server 2005, install the June CTP, and attach your database files to the server.

After Beta 2 of SQL Server 2005, we have made two changes that impact XML indexes. First, string comparisons on XML data type use a binary collation. Secondly, a bug in the key fields of the secondary XML indexes has been fixed. If you have created XML indexes using the Beta 2 build, you will find the XML indexes are disabled after the upgrade. If you have created the XML indexes using post Beta 2 builds, or already upgraded to a post Beta 2 build and rebuilt your XML indexes, you should not face this issue.

To rebuild your XML indexes, use the following steps:

1. Check whether your XML indexes are disabled after the upgrade with the query below:

SELECT count(*)

FROM sys.xml_indexes

WHERE is_disabled != 0;

If the query returns 0, then your XML indexes are not disabled and you do not need to do anything.

2. Otherwise, enable (rebuild) the primary and secondary XML indexes. The primary XML indexes must be rebuilt before the secondary XML indexes

a. Determine the primary XML indexes in a database:

SELECT sxi.name "Index name", so.name "Table name"

FROM sys.xml_indexes sxi JOIN sys.objects so

ON (so.object_id = sxi.object_id)

WHERE using_xml_index_id IS NULL;

b. Rebuild the primary XML indexes:

ALTER INDEX <primary_xml_index> ON <table_name>

REBUILD;

c. Determine the secondary XML indexes in a database:

SELECT sxi.name "Index name", so.name "Table name"

FROM sys.xml_indexes sxi JOIN sys.objects so

ON (so.object_id = sxi.object_id)

WHERE using_xml_index_id IS NOT NULL;

d. Then rebuild the secondary XML indexes:

ALTER INDEX <secondary_xml_index> ON <table_name>

REBUILD;

A few additional notes:

· The index options specified during the creation of these XML indexes will be preserved when you use ALTER INDEX … REBUILD.

· Ana (tester) and Mark (developer) pointed out that a faster mechanism is to drop the XML indexes first and then to recreate them. This also requires less disk space, even compared to CREATE XML INDEX … WITH DROP_EXISTING. Do the following:

a. Make a note of the index options using

SELECT * FROM sys.xml_indexes

b. Drop the primary XML indexes – this will drop the secondary XML indexes as well

DROP INDEX <primary_xml_index> ON <table_name>

c. Recreate the primary and secondary XML indexes with the desired index options.

· Using ALTER INDEX ALL ON <table_name> REBUILD could be used – it figures out the order in which the primary XML indexes must be rebuilt. However, it rebuilds all the indexes on <table_name> – both XML and non-XML ones – and will take longer.

· If you want to use SQL Server Management Studio to rebuild the XML indexes, see the topic “How to: Rebuild an Index (SQL Server Management Studio)” in SQL Server 2005 Books Online.

I hope this information helps you with Beta 2 to June CTP upgrade.

Thank you,

Shankar

Program Manager

Microsoft SQL Server

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

Use of included script samples are subject to the terms specified at http://www.microsoft.com/info/cpyright.htm

MSDN whitepapers for native XML support in SQL Server 2005

SPal — Wed, 29 Jun 2005 00:53:00 GMT

SQL Server 2005 June CTP was released earlier this month. It contains many improvements and is a very important milestone on the way to RTM. If you haven’t upgraded yet, please do so! For the native XML support, I’d like to point out the following.

MSDN whitepapers:

We’ve updated the MSDN whitepapers and added new ones. Here are the links:

XML feature overview: http://msdn.microsoft.com/xml/default.aspx?pull=/library/en-us/dnsql90/html/sql2k5xml.asp

XML Best Practices: 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

XML Options in Microsoft SQL Server 2005: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsql90/html/sql2k5xmloptions.asp

Introduction to XQuery in SQL Server 2005: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsql90/html/sql2k5_xqueryintro.asp

The XML optimizations and XML best practices whitepapers in particular have much more content – some of the new optimizations are very cool! Check these out by following the appropriate links.

When you read these whitepapers, please take a moment to rate their content and their presentation.

Enjoy!

Thank you,

Shankar

Program Manager

Microsoft SQL Server

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

Eliminating Multiple Evaluations of XML Data Type Methods

SPal — Wed, 06 Apr 2005 20:57:00 GMT

I have seen a few scenarios in which a value is extracted from an XML data type instance in SQL Server 2005. The query performs some checks on the value such as its type (e.g. whether it is numeric) or compares it with a constant, and returns a value based on this check. The value extraction is done using the value() method of XML data type, and the method is re-evaluated in the SELECT list. I want to share a simple tip for better performance. Consider the example

DECLARE @x XML
SET   @x = '<book ISBN="0-7356-1588-2">
                  <title>Writing Secure Code</title>
                  <subject/>
                  <price>39.99</price>
            </book>'

The price of the book can be retrieved using the following query as nvarchar(32) if it is not known for sure that it is actually a numeric value in all <book> instances:

SELECT @x.value ('(/book/price)[1]', 'nvarchar(32)')

Suppose the query then wants to convert it to a decimal value if it is numeric and return 0 if it is not. The full query then becomes:

SELECT case isnumeric(@x.value ('(/book/price)[1]', 'nvarchar(32)'))
       when 1 then @x.value ('(/book/price)[1]', 'decimal(5,2)')
              else 0
       end

This query computes the value() method twice. A simple trick avoids the recomputation by assigning the result of @x.value ('/book/price', 'nvarchar(32)') to a SQL variable of type nvarchar(32) and converting the variable to decimal:

DECLARE @v nvarchar(32)
SET   @v = (SELECT @x.value ('(/book/price)[1]', 'nvarchar(32)'))
SELECT case isnumeric(@v)
       when 1 then CAST (@v AS decimal(5,2))
              else 0
       end

The rewrite performs significantly faster than the earlier query since it manually optimizes the query to reuse computed values. It also simplifies the query plan quite a bit. There is an underlying assumption on its benefit– the majority of the <price> values are numeric, otherwise the workload does not perform much faster.

Often, there are many more values you want to extract for the XML instance, and breaking up the query into a separate one for each variable assignment is inconvenient. The query may also involve the nodes() method, so that breaking up the query increases the number of nodes() method invocations and requires table-valued variables - the benefits are then lost. A subquery comes to our rescue! Look at the following rewrite in which the value() method is computed in a subquery and aliased as T(Price) and reused in the outer SELECT:

SELECT case isnumeric(Price)
       when 1 then CAST (Price AS decimal(5,2))
              else 0
       end
FROM (SELECT @x.value ('(/book/price)[1]', 'nvarchar(32)') Price) T

You get the same benefits as before, ignoring the difference between the variable assignment and the subquery costs, which are much smaller than the cost of the value() method computation. The same optimization can be used in other places as well:

SELECT NULLIF (Subj, '')
FROM (SELECT @x.value ('(/book/subject)[1]', 'nvarchar(64)') Subj) T

The value() method returns the empty string '' for subject, the NULLIF compares the returned value with its second argument '' and returns NULL since these two values are equal. Replacing Subj with the value() method in NULLIF (Subj, ''), as shown below, computes the value() method twice when the return value is other than the empty string. This double computation is much slower:

SELECT NULLIF (@x.value ('(/book/subject)[1]', 'nvarchar(64)'), '')

You get the idea. We can put the two queries together as follows:

SELECT case isnumeric(Price)
            when 1 then CAST (Price AS decimal(5,2))
              else 0
            end,
       NULLIF (Subj, '')
FROM (SELECT @x.value ('(/book/price)[1]', 'nvarchar(32)') Price,
              @x.value ('(/book/subject)[1]', 'nvarchar(64)') Subj
       ) T

You might wonder – why doesn’t the query optimizer do this trick? It certainly is an option and hey – if we did it all in one release, what would we do in the future? ;-)

Best wishes and thank you,

Shankar
Program Manager
Microsoft SQL Server

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

Use of included script samples are subject to the terms specified at http://www.microsoft.com/info/cpyright.htm

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.