Introduction to XML CS348 Information System Guest Lecture Hazem Elmeleegy

Outline What is XML?

Syntax of XML Document

DTD (Document Type Definition)

XML Query Language

XML Databases

XML Schema

Oracle JDBC

Introduction to XMLXML 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 XMLElements (Tags) are the primary components of XML documents. JAMES RUSSEL

Element FNAME nested inside element Author.Attributes provide additional information about Elements. Values of the Attributes are set inside the Elements Element Author with Attr idComments stats with

XML DTDA 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. cXML Document is valid if it has an attached DTD and document is structured according to rules defined in DTD.

DTD Example

RICHRD KARTER

LASTNAME(#PCDATA)>

]>

Xml Document And Corresponding DTD

XML SchemaServes same purpose as database schemaSchemas are written in XMLSet of pre-defined simple types (such as string, integer)Allows creation of user-defined complex types

XML SchemaRDBMS Schema (s_id integer, s_name string, s_status string)

Allan62allan@abc.com

XMLSchema

XML Document and Schema

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

XQueryXQuery 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

John22jhn@xyz.com

XPath: /Student[Name=John]/EmailExtracts: element with value jhn@xyz.com

Oracle and XMLXML Support in Oracle

XDK (XML Developer Kit) XML Parser for PL/SQL XPath XSLT

Oracle and XMLXML documents are stored as XML Type ( data type for XML ) in OracleInternally CLOB is used to store XMLTo store XML in database create table with one XMLType columnEach row will contain one of XML records from XML documentDatabase Table: XML DocumentDatabase Row : XML Record

Examples

John120 Northwestern AvePaul120 N. Salisbury

ExampleCreate table prTable(patientRecord XMLType);DECLAREprXML CLOB;BEGIN-- Store Patient Record XML in the CLOB variableprXML := '

ExampleTO PRINT PATIENT ID of ALL PATIENTS

SELECT EXTRACT(p.patientRecord, '/Patient/@id').getStringVal()FROM prTable p;

USE XPATH

Oracle JDBCJDBC an API used for database connectivityCreates Portable ApplicationsBasic Steps to develop JDBC ApplicationImport JDBC classes (java.sql.*).Load JDBC driversConnect and Interact with database Disconnect from database

Oracle JDBCDriverManager provides basic services to manage set of JDBC driversConnection object sends queries to database server after a connection is set upJDBC provides following three classes for sending SQL statements to server

Statement SQL statements without parametersPreparedStatement SQL statements to be executed multiple times with different parametersCallableStatement Used for stored procedures

Oracle JDBCSQL query can be executed using any of the objects. (Statement,PreparedStatement,CallableStatement)Syntax (Statement Object )Public abstract ResultSet executeQuery(String sql) throws SQLExceptionSyntax (PreparedStatement,CallableStatement Object )Public abstract ResultSet executeQuery() throws SQLExceptionMethod 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[1] Database Management Systems by Ramakrishnan and Gehrke

Thank You