Download Introduction to XML

Introduction to XML
CS348 Information System
Guest Lecture
Hazem Elmeleegy
Outline
 What is XML?
 Syntax of XML Document
 DTD (Document Type Definition)
 XML Schema
 XML Query Language
 XML Databases
 Oracle JDBC
Introduction to XML
 XML stands for EXtensible Markup Language
 XML was designed to describe data.
 XML tags are not predefined unlike HTML
 XML DTD and XML Schema define rules to
describe data
 XML example of semi structured data
Building Blocks of XML
 Elements (Tags) are the primary components of XML
documents.
Element FNAME nested inside
<AUTHOR id = 123>
element Author.
Element
<FNAME> JAMES</FNAME>
Author with
<LNAME> RUSSEL</LNAME>
Attr id </AUTHOR>
<!- I am comment ->
 Attributes provide additional information about Elements.
Values of the Attributes are set inside the Elements
 Comments stats with <!- and end with ->
XML DTD
 A DTD is a set of rules that allow us to specify
our own set of elements and attributes.
 DTD is grammar to indicate what tags are
legal in XML documents. c
 XML Document is valid if it has an attached
DTD and document is structured according to
rules defined in DTD.
DTD Example
<BOOKLIST>
<BOOK GENRE = “Science”
FORMAT = “Hardcover”>
<AUTHOR>
<FIRSTNAME>
RICHRD
</FIRSTNAME>
<LASTNAME> KARTER
</LASTNAME>
</AUTHOR>
</BOOK>
</BOOKS>
Xml Document And
Corresponding DTD
<!DOCTYPE BOOKLIST[
<!ELEMENT BOOKLIST(BOOK)*>
<!ELEMENT BOOK(AUTHOR)>
<!ELEMENT
AUTHOR(FIRSTNAME,LASTNAM
E)>
<!ELEMENT
FIRSTNAME(#PCDATA)>
<!ELEMENT>LASTNAME(#PCDATA)
>
<!ATTLIST BOOK GENRE
(Science|Fiction)#REQUIRED>
<!ATTLIST BOOK FORMAT
(Paperback|Hardcover)
“PaperBack”>]>
XML Schema
 Serves same purpose as database schema
 Schemas are written in XML
 Set of pre-defined simple types (such as
string, integer)
 Allows creation of user-defined complex
types
XML Schema
 RDBMS Schema (s_id integer, s_name string, s_status string)
 XMLSchema
<xs:schema>
<xs:complexType name = “StudnetType”>
<xs:attribute name=“id” type=“xs:string” />
<xs:element name=“Name” type=“xs:string />
<xs:element name=“Age” type=“xs:integer” />
<xs:element name=“Email” type=“xs:string” />
</xs:complexType>
<xs:element name=“Student”
type=“StudentType” />
XML Document and Schema </xs:schema>
<Students>
<Student id=“p1”>
<Name>Allan</Name>
<Age>62</Age>
<Email>[email protected]
</Email>
</Student>
</Students>
XML Query Languages
 Requirement
Same functionality as database query
languages (such as SQL) to process Web
data
 Advantages
 Query selective portions of the document (no
need to transport entire document)
 Smaller data size mean lesser
communication cost
XQuery
 XQuery to XML is same as SQL to
RDBMS
 Most databases supports XQuery
 XQuery is built on XPath operators
(XPath is a language that defines path
expressions to locate document data)
XPath Example
<Student id=“s1”>
<Name>John</Name>
<Age>22</Age>
<Email>[email protected]</Email>
</Student>
XPath: /Student[Name=“John”]/Email
Extracts: <Email> element with value
“[email protected]”
Oracle and XML
 XML Support in Oracle
XDK (XML Developer Kit)
XML Parser for PL/SQL
XPath
XSLT
Oracle and XML
 XML documents are stored as XML Type ( data type
for XML ) in Oracle
 Internally CLOB is used to store XML
 To store XML in database create table with one
XMLType column
 Each row will contain one of XML records from XML
document
 Database Table:
 Database Row :
XML Document
XML Record
Examples
<Patients>
<Patient id=“p1”>
<Name>John</Name>
<Address>
<Street>120 Northwestern Ave</Street>
</Address>
</Patient>
<Patient id=“p2”>
<Name>Paul</Name>
<Address>
<Street>120 N. Salisbury</Street>
</Address>
</Patient>
</Patients>
Example
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Create table prTable(patientRecord XMLType);
DECLARE
prXML CLOB;
BEGIN
-- Store Patient Record XML in the CLOB variable
prXML := '<Patient id=“p1">
<Name>John</Name>
<Address>
<Street>120 Northwestern Ave</Street>
</Address>
</Patient>‘ ;
-- Now Insert this Patient Record XML into an XMLType column
INSERT INTO prTable (patientRecord) VALUES
(XMLTYPE(prXML));
 END;
Example
TO PRINT PATIENT ID of ALL PATIENTS
SELECT
EXTRACT(p.patientRecord,
'/Patient/@id').getStringVal()
FROM prTable p;
USE XPATH
Oracle JDBC
 JDBC an API used for database connectivity
 Creates Portable Applications
 Basic Steps to develop JDBC Application
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Import JDBC classes (java.sql.*).
Load JDBC drivers
Connect and Interact with database
Disconnect from database
Oracle JDBC
 DriverManager provides basic services to
manage set of JDBC drivers
 Connection object sends queries to database
server after a connection is set up
 JDBC provides following three classes for
sending SQL statements to server
 Statement SQL statements without parameters
 PreparedStatement SQL statements to be executed
multiple times with different parameters
 CallableStatement Used for stored procedures
Oracle JDBC
 SQL query can be executed using any of the
objects.
(Statement,PreparedStatement,CallableStatement)
 Syntax (Statement Object )
Public abstract ResultSet executeQuery(String sql) throws
SQLException
 Syntax (PreparedStatement,CallableStatement Object )
Public abstract ResultSet executeQuery() throws SQLException
 Method executes SQL statement that returns
ResultSet object (ResultSet maintains cursor
pointing to its current row of data. )
Oracle JDBC (Example)
Import java.sql.*;
Import java.io;
Class simple{
public static void main(String[] args) throws Exception{
Connection conn=null;
try{
String conStr = "jdbc:oracle:thin:@oracle.cs.purdue.edu:1521:orb";
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
conn = DriverManager.getConnection(conStr,”username”,”passwd");
Statement cursor = conn.createStatement(); // Connection Est.
ResultSet rset = stmt.executeQuery(“Select* from table_name”);
while(orset.next()){
System.out.println(“Printing column name ”+orest.getStringVal(1));
}
}Catch(ClassNotFoundException e){}
cursor.close();
conn.close();
}
References
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[1] Database Management Systems by Ramakrishnan and Gehrke
Thank You