SQL/XML on Oracle

SQL/XML on Oracle
Kristian Torp
Department of Computer Science
Aalborg University
people.cs.aau.dk/˜torp
torp@cs.aau.dk
November 26, 2015
daisy.aau.dk
Kristian Torp (Aalborg University) SQL/XML on Oracle November 26, 2015 1 / 73

Outline
1 Introduction
2 From Tables to XML
Introduction
SQL/XML Publishing Functions
Quick and Dirty Publishing Functions
XML View on Relational Data
3 The XML Data Type
Introduction
oradb: Protocol
4 From XML to Tables
Introduction
A Simple Example
A Longer Example
5 Summary

Learning Goals
Goals
Overview of SQL/XML
Extract relational information as XML
Introduction querying XML on PostgreSQL
Note
SQL/XML is part of the SQL standard
SQL/XML is being supported by the major DBMS vendors
It has nothing to do with SQLXML from Microsoft
Standard
Concepts are general
Code is sometimes DBMS speciﬁc

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Overall Picture
The Main Idea
SQL/XML query <stuff></stuff>
Note
SQL/XML is an SQL extension
Added in 2003, extended in 2008 and 2011 versions of SQL
SQL/XML is bidirectional from tables to XML
Started as tables to XML
Extended with XML to tables
The major DBMS vendors do not agree on the SQL/XML syntax!

XPath and XQuery vs. SQL/XML
XPath and XQuery
XPath and XQuery are XML
centric

XPath and XQuery vs. SQL/XML
XPath and XQuery
XPath and XQuery are XML
centric
SQL/XML
SQL/XML is SQL centric

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Create Relational Schema
Example (Create the Table)
create table course (
id i n t primary key ,
name varchar2 (50) not null ,
semester i n t not null ,
descr varchar2 (255) not n u l l
) ;
Example (Load the Data)
i n s e r t i n t o course values
(4 , ’OOP’ , 3 , ’ Object−oriented programming ’ ) ;
i n s e r t i n t o course values
(2 , ’DB ’ , 7 , ’ Databases including SQL ’ ) ;

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Introduction: SQL/XML
Steps
Main purpose to map between XML and SQL
A wrapper layer
A standard deﬁned by the ISO/ANSI SQL committee
Part 14 of of SQL 2003

Get XML Out, First Try
Example (Query One)
select XMLElement ( ” course ” ,
XMLAttributes ( id as ” id ” ) ,
XMLElement ( ”name” , name) ,
XMLElement ( ” semester ” , semester ) ,
XMLElement ( ” desc ” , descr ) )
from course ;
Note
It is a select statement!
The SQL/XMLpublishing functions XMLElement and XMLAttributes.
It is fairly easy to guess what it does!

First Result
Example (Result Query One)
<course id=” 4 ”>
<name>OOP</name>
<semester>3</ semester>
<desc>Object−oriented programming</ desc>
</ course>
<name>DB</name>
<desc>Databases including SQL</ desc>
</ course>
Note
Not a well-formed XML document! Why?

Get XML Out, Adding a Root Element
Example (Query Two)
select XMLElement ( ” coursecatalog ” ,
XMLAgg( XMLElement ( ” course ” ,
XMLElement ( ” desc ” , descr ) ) ) )
from course ;
Note
The XMLAgg another publishing function
XMLAgg is an aggregate function like min, max, and avg
XMLAgg has optional order by clause

Second Result
Example (Result Query Two)
<coursecatalog>
<name>OOP</name>
</ course>
<name>DB</name>
</ course>
</ coursecatalog>
Note
Now the XML document has a root element
Still missing the processing instructions at the top

Get XML Out, Adding XML Deﬁnition
Example (Query Three)
select XMLRoot(
( select XMLElement ( ” coursecatalog ” ,
from course ) , VERSION ’ 1.0 ’ )
from dual ;
Note
It is now a nested statement

Third Result
Example (Result Query Three)
<?xml version=” 1.0 ” standalone=” yes ” ?>
<coursecatalog>
<name>OOP</name>
</ course>
<name>DB</name>
</ course>
</ coursecatalog>
Note
Got the XML header

Get XML Out, Adding an XSLT
Example (Query Four)
select XMLRoot(
XMLConcat
(
XMLPI(NAME ” xml−stylesheet ” , ’ type =” t e x t / xsl ”
href = ” . . / x s l t / coursecatalog . x s l t ” ’ ) ,
(
from course
)
) ,
VERSION ’ 1.0 ’ ) from dual ;

Final Result
Example (Result Query Four)
<?xml version=” 1.0 ” ?>
<?xml−stylesheet type=” t e x t / xsl ”
href=” . . / x s l t / coursecatalog . x s l t ” ?>
<coursecatalog>
<name>OOP</name>
</ course>
<name>DB</name>
</ course>
</ coursecatalog>
Note
A nice valid XML document!

Overview
Function Description
XMLRoot Creates a root node
XMLElement Creates an XML element
XMLAttributes Creates attributes on elements
XMLAgg Aggregates XML fragments
XMLForest Creates a forest of elements
XMLConcat Appends elements
XMLPI Create processing instructions
XMLComment Create comments
Note
These are all standard publishing functions
The uses/misuse of abbreviations

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Quick and Dirty
Example (Shortest Possible)
select XMLForest ( id , name, semester , descr )
from course
Example (The Result)
<ID>4</ ID><NAME>OOP</NAME><SEMESTER>3</SEMESTER><DESCR> . . . </DESCR>
<ID>2</ ID><NAME>DB</NAME><SEMESTER>7</SEMESTER><DESCR> . . . </DESCR>
Note
Two rows are returned
Element names are in upper case (Oracle/SQL default)
No container element for each row

Quick and Dirty
select XMLForest ( ∗ )
from course
Note
Not allowed on Oracle

Quick and Dirty
select XMLForest ( ∗ )
from course
Note
Not allowed on Oracle
select XMLForest ( co . ∗ )
from course co
Note
Not allowed either!

Rename Columns
Example (Rename Columns)
select XMLForest ( ID as ” id ” ,
name as ” course−name” ,
semester as ” semester ” ,
descr as ” description ” )
from course
<id>4</ id><course−name>OOP</ course−name><semester>3</ semester> . . .
<id>2</ id><course−name>DB</ course−name><semester>7</ semester> . . .
Note
Must use double quote ” and not single quote
As is optional if scalar value

Added Outer Element
Example (A Tag for Each Row)
select XMLElement (
” course ” ,
XMLForest ( ID as ” id ” ,
name as ” course−name” ,
semester as ” semester ” ,
descr as ” description ” ) )
from course
<course><id>4</ id><course−name>OOP</ course−name> . . . </ course>
<course><id>2</ id><course−name>DB</ course−name> . . . </ course>
Note
Still two rows being returned
The wrapping of each row

Quick and Dirty, cont
Example (With Projection)
select XMLForest ( id , name, semester )
from course
<ID>4</ ID><NAME>OOP</NAME><SEMESTER>3</SEMESTER>
<ID>2</ ID><NAME>DB</NAME><SEMESTER>7</SEMESTER>

Quick and Dirty, cont
Example (With Projection)
select XMLForest ( id , name, semester )
from course
<ID>4</ ID><NAME>OOP</NAME><SEMESTER>3</SEMESTER>
<ID>2</ ID><NAME>DB</NAME><SEMESTER>7</SEMESTER>
Example (With Projection and Renaming)
select XMLForest ( id as ” cid ” , name ” coursename ” )
from course
<cid>4</ cid><coursename>OOP</ coursename>
<cid>2</ cid><coursename>DB</ coursename>
Note
Filtering (selection) is possible in the where clause

Quick and Dirty, cont I
Example (With Element per Row)
select XMLElement (name ” course ” ,
XMLForest ( id as ” cid ” , name as ”cname” ) )
from course
<course><cid>4</ cid><cname>OOP</ cname></ course>
<course><cid>2</ cid><cname>DB</ cname></ course>

Quick and Dirty, cont II
Example (With Root Element)
XMLAgg(
XMLElement ( ” course ” ,
XMLForest ( id as ” cid ” , name as ”cname” ) ) ) )
from course
<coursecatalog>
<course><cid>4</ cid><cname>OOP</ cname></ course>
<course><cid>2</ cid><cname>DB</ cname></ course>
</ coursecatalog>

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

XMLType Views
Example (Create an XML view on an existing table)
create or replace view course xml of XMLType with object id
( e x tract
( object value , ’ / coursecatalog / course / @id ’ ) . getnumberval ( ) )
as select XMLElement ( ” coursecatalog ” ,
from course ;
Note
A create view statement
Use the SQL/XML publishing functions

XQuery on Oracle I
Example (Get info on the OOP course)
XQUERY
f o r $c in ora : view ( ” course xml ” ) / coursecatalog / course
where $c /name=”OOP”
return $c
Example (Result)
column value
<name>OOP</name>
<desc>Object−oriented Programming</ desc>
</ course>

XQuery on Oracle II
Example (Count the number of courses)
XQUERY
f o r $c in ora : view ( ” course xml ” ) / coursecatalog
l e t $cour := count ( $c / course )
return $cour
Example (Result)
column value
2
Note
Remember ’/’ to execute from command line

Summary: Tables to XML
Summary
SQL/XML is an ISO/ANSI standard not part of W3C
Oracle has made vendor speciﬁc extensions to SQL/XML
SQL/XML is good for mapping SQL to XML
It is often very convenient to be able to do the mapping in plain SQL
Start building SQL/XML queries from the inside and out
Alternatives to SQL/XML
Store XML in native format in the database
DBMS vendor speciﬁc extension, e.g. DBMS XMLGEN
Do SQL to XML in programming language

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Introduction
Example (The Best of Both Worlds)
Id Txt
1 <course id=’22’><name>OOP</name></course>
2 <course id=’11’><name>DB</name></course>
3 <course id=’33’><name>SQL</name></course>
SQL and XML
Store XML as any other data type in a table
Retain possiblity to use SQL for querying data
Be able to query the XML data using XPath and XQuery
Conversion of XML to SQL
Retain pure SQL view on all data

The coursecat Table
Example
id dsc exercises
11
<course cid=” 11 ”>
<name>Database</name>
</ course>
22
<name>OOP</name>
</ course>
<exercises>
<exercise eid=” 1 ”>
<desc>What i s OOP?</ desc>
<answer> I t . . . </ answer>
</ exercise>
</ exercises>
23
<name>SQL</name>
</ course>
<exercises>
<desc>What i s SQL?</ desc>
</ exercise>
<desc>What i s a query?</ desc>
</ exercise>
</ exercises>

Create Relational Schema
Example (Create the Table)
create table coursecat (
id i n t primary key ,
dsc xmltype not null ,
exercises xmltype
) ;
Example (Load the Data)
i n s e r t i n t o coursecat values (
22 ,
’<course cid =”22”>
<name>OOP</name>
</course> ’ ,
’<exercises >
<exercise eid =”1”>
<desc>What i s OOP?</desc>
<answer> I t . . . < / answer>
</ exercise >
</ exercises > ’
) ;

Say Hello
Example (Hello, World!)
select XMLQuery( ’
l e t $s := ” Hello , World ! ”
return $s ’ returning content ) as o
from dual ;
Example (Result)
o
Hello, World!
Note
The XMLQuery function
The XQuery in a string
The returning content is required
The alias (o) is optional (otherwise ugly column name)

Simple XPath
Example (Use SQL and XPath)
select id , xmlquery ( ’ / / exercise ’
passing exercises
returning content ) as res
from coursecat
Example (Result)
ID RES
11
22 (XMLTYPE)
23 (XMLTYPE)
Note
Passing by value exercises
Return value is of the XMLType data type

Extracting Values
Example (extractvalue Function)
select id ,
extractvalue ( dsc , ’ / / course /name/ t e x t ( ) ’ ) as course name
from coursecat
Example (Result)
ID COURSE NAME
11 Database
22 OOP
23 SQL
Note
The extracevalue function is Oracle speciﬁc
//course/name will do the same
//course will fail (more than one node)!

Extracting Multiple Values
Example (XML to SQL)
select id ,
extractvalue ( dsc , ’ / / course / @cid ’ ) as course id ,
extractvalue ( dsc , ’ / / course /name/ t e x t ( ) ’ ) as course name
from coursecat
Example (Result)
ID COURSE ID COURSE NAME
11 11 Database
22 22 OOP
23 33 SQL
Note
Attributes and elements extract in the same manner
Now have a pure relational access to data
Can ﬁlter on COURSE ID in a where clause

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Extracting Content Directly from XML
Example (XMLQuery Function)
select
xmlquery ( ’ f o r $doc in
fn : c o l l e c t i o n ( ” oradb : / PUBLIC /COURSECAT/ROW/DSC” )
return $doc ’ returning content )
from dual
Example (Result)
XMLQUERY(. . .)
<course cid=”11”><name>Database</name>... </course>
Note
All in upper case
PUBLIC if table is available to current user
ROW is required in the XPath

From SQL Directly
Example (XQUERY SQL∗Plus Keyword)
XQUERY
f o r $doc in c o l l e c t i o n ( ” oradb : / PUBLIC /COURSECAT/ROW/EXERCISES” )
where $doc / / exercise / @eid = 1
return $doc
Example (Result)
COLUMN VALUE
<exercises><exercise eid=”1”><desc>What is OOP?</desc>...
Note
XQUERY not XMLQuery
The collection is the fn:collection method

Summary: XML Data Type
Summary
XMLQuery is part of the SQL standard
Allows full XQuery
In princip XQuery on XML ﬁle in Oracle!
Oracle as a pure XQuery engine
Supported by DB2 and Oracle
Data type other name (xml) on SQL Server
Oracle made extensions to support SQL∗Plus

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

The Overall Idea
The Flow
XMLTable query <stuff></stuff>
Note
XMLTable is a part of SQL/XML
XMLTable returns a rowset
It is a table function
Overview SQL/XML Functions
SQL Clause SQL/XML Function
select XMLQuery
from XMLTable
where XMLExists

The coursecat Table
Example
id dsc exercises
11
<name>Database</name>
</ course>
22
<name>OOP</name>
</ course>
<exercises>
<desc>What i s OOP?</ desc>
</ exercise>
</ exercises>
23
<name>SQL</name>
</ course>
<exercises>
<desc>What i s SQL?</ desc>
</ exercise>
<desc>What i s a query?</ desc>
</ exercise>
</ exercises>

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

From XML to SQL
Example (Get the Course Name)
select id , course name
from coursecat ,
XMLTable ( ’ / course ’ passing dsc
columns course name varchar2 (10) path ’name ’ )
Example (Result)
ID COURSE NAME
11 Database
22 OOP
23 SQL
Note
The passing, columns, and path keywords
/course is the row pattern, here XPath full XQuery supported
name is the column pattern, here XPath full XQuery supported

More Advanced XPath
Example (Multiple XML Columns)
select id , course name , no exercises
from coursecat ,
columns course name varchar2 (10) path ’name ’ ) ,
XMLTable ( ’ / exercises ’ passing exercises
columns no exercises i n t path ’ count ( exercise ) ’ )
Example (Result)
ID COURSE NAME NO EXERCISES
22 OOP 1
23 SQL 2
Note
Multiple XMLTable calls
No join condition, recall implicitely joined
Advanced path expressions count(exercise)

Using in the Where Clause
Example (Find where IDs are not Matching)
select id , course id , course name
from coursecat ,
columns course id i n t path ’@cid ’ ,
course name varchar2 (10) path ’name ’ )
where id != course id
Example (Result)
ID COURSE ID COURSE NAME
23 33 SQL
Note
Attribute used in column pattern: @cid
Element used in column pattern: name
Comparison in where clause

Ordinality and Default Value
Example (Find where IDs are not Matching)
select coursecat . id , num, exercise id , author
from coursecat ,
XMLTable ( ’ / exercises / exercise ’
passing exercises
columns
num f o r o r d i n a l i t y ,
exercise id i n t path ’@eid ’ ,
author varchar2 (30) path ’ author ’ default ’ Ib ’
Example (Result)
ID NUM EXERCISE ID AUTHOR
22 1 1 Ib
23 1 1 Ib
23 2 11 Ib

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

Information on Course ID and Name I
Example
select coursecat . id , x . course name
from coursecat ,
XMLTable ( ’ / course ’
passing coursecat . dsc
columns
course name varchar2 (30) path ’ / course /name ’ ) x
Example (Result)
id course name
11 Database
22 OOP
23 SQL

Information on Course ID and Name II
Example
select coursecat . id , x . course name
from coursecat ,
XMLTable ( ’ / course ’
columns
course name varchar2 (30) path ’ / course /name ’ ) x
Note
Displays relation data along side XML data!
Implicit join
Columns explicitely named and typed
XMLTable alias (x) is optional
The XPath expression in columns can only return one item (per row)!
/course can be simpliﬁed to (/)

Information on Course ID, Name, and Exercises I
Example
select coursecat . id , course name , exercise id
from coursecat ,
XMLTable ( ’ / ’
passing coursecat . dsc −− table −name. column−name
columns
course name varchar2 (30) path ’ / / name ’ ) ,
passing exercises −− only column name
columns
exercise id i n t path ’ / exercises / exercise [ 1 ] / @eid ’ )
Example (Result)
id course name exercise id
22 OOP 1
23 SQL 1

Information on Course ID, Name, and Exercises II
Example
select coursecat . id , course name , exercise id
from coursecat ,
passing coursecat . dsc −− table −name. column−name
columns
passing exercises −− only column name
columns
exercise id i n t path ’ / exercises / exercise [ 1 ] / @eid ’ )
Note
Multiple XMLTable functions
Both elements and attributes are converted to tabular
The use of absolute and relative paths
Must select ﬁrst exercise otherwise error

Information on Course ID, Name, and Exercises, cont I
Example
select coursecat . id , course name , exercise id , descr , answer
from coursecat ,
columns
passing exercises
columns
descr varchar2 (30) path ’ desc ’ ,
answer varchar2 (30) path ’ answer ’ )

Information on Course ID, Name, and Exercises, cont II
Example (Result)
id course name exercise id descr answer
22 OOP 1 What is OOP? It ...
23 SQL 1 What is SQL? It ...
23 SQL 11 What is a query? It ...

Information on Course ID, Name, and Exercises, cont III
Example
from coursecat ,
columns
passing exercises
columns
answer varchar2 (30) path ’ answer ’ )
Note
Change the XPath for exercises to a lower level
Missing information on one course

Information on Course ID, Name, and Exercises, cont I
Example
from coursecat ,
columns
course name varchar2 (30) path ’ / / name ’ )
l e f t outer j o i n
passing exercises
columns
answer varchar2 (30) path ’ answer ’ ) on 1=1

Information on Course ID, Name, and Exercises, cont II
Example (Result)
id course name exercise id descr answer
11 Database
22 OOP 1 What is OOP? It ...
23 SQL 1 What is SQL? It ...
23 SQL 11 What is a query? It ...

Information on Course ID, Name, and Exercises, cont III
Example
from coursecat ,
columns
course name varchar2 (30) path ’ / / name ’ )
l e f t outer j o i n
passing exercises
columns
answer varchar2 (30) path ’ answer ’ ) on 1=1
Note
The left outer join between the two XMLTable function calls
The on clause on 1=1

Filtering Based on XML Content I
Example
select x .∗
from coursecat , XMLTable ( ’ / exercises / exercise ’
passing exercises
columns
answer varchar2 (30) path ’ answer ’ ) x
Example (Result)
exercise id descr answer
1 What is OOP? It ...
1 What is SQL? It ...
11 What is a query? It ...
Note
Too much information, i.e., no ﬁltering

Filtering Based on XML Content II
Example
select x .∗
from coursecat , XMLTable ( ’ / exercises / exercise ’
passing exercises
columns
answer varchar2 (30) path ’ answer ’ ) x
where XMLExists ( ’ / exercises / exercise [ @eid=11] ’ passing exercises )
Example (Result)
exercise id descr answer
1 What is SQL? It ...
11 What is a query? It ...
Note
The XMLExist for ﬁltering in XML content

Summary: XML to Tables
Summary
The core function is XMLTable
Supported on most DBMS
Explicit naming
Cannot guess SQL column names element/attributes
Explicit typing
Cannot guess SQL data types from XML document
Result of XMLTable can be joined like other tables!
Literature
XMLTABLE by example, Part 1
Walk-through on how to handle multiple rows (ﬁve diff. ways)
www.ibm.com/developerworks/data/library/techarticle/
dm-0708nicola/
XMLTABLE by example, Part 2
On scredding large XML documents plus insert relational from XML
www.ibm.com/developerworks/data/library/techarticle/
dm-0709nicola/Kristian Torp (Aalborg University) SQL/XML on Oracle November 26, 2015 69 / 73

Outline
1 Introduction
Introduction
3 The XML Data Type
Introduction
oradb: Protocol
Introduction
A Simple Example
A Longer Example
5 Summary

SQL/XML vs. XPath/XQuery
SQL/XML
SQL centric
Small extension to SQL
null well understood
No implicit order
Bad support hierarchies
XPath/XQuery
XML centric
New programming languages
Handling of null be aware!
Ordering (a sequence)
Excellent support hierarchies

SQL/XML vs. XPath/XQuery
SQL/XML
SQL centric
Small extension to SQL
null well understood
No implicit order
Bad support hierarchies
XPath/XQuery
XML centric
New programming languages
Handling of null be aware!
Ordering (a sequence)
Excellent support hierarchies
Note
SQL/XML and XQuery serve different purposes
Are not competing technologies!

Summary
Main Points
SQL/XML is an ISO/ANSI standard
SQL/XML example of wrapper technology
Make table look like XML documents
Well integrated into PostgreSQL, Oracle, and other DBMSs
XML data type is much smarter than a CLOB
Must look elsewhere for XML to tables
Standards
SQL/XML publishing functions added in SQL/XML:2003
XMLExists, XMLQuery, and XMLTable added in SQL/XML:2006
SQL/XML standardization faster than overall SQL standardization

Additional Information
Web Sites
Good SQL/XML tutorial
www.stylusstudio.com/sqlxml_tutorial.html
Advancements in SQL/XML www.sigmod.org/sigmod/record/
issues/0409/11.JimMelton.pdf
Jim Melton in SIGMOD Record
PostgreSQL and XML http:
//www.slideshare.net/petereisentraut/postgresql-and-xml
Slightly outdated, but good
Oracle’s XML Technology Center
www.oracle.com/technology/tech/xml/index.html
Get off to a fast start with DB2 9 pureXML
http://www.ibm.com/developerworks/data/library/
techarticle/dm-0603saracco2/
Part of series of papers on XML support on DB2

SQL/XML on Oracle

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