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 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. 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 id Comments stats 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 RICHRD KARTER <!DOCTYPE BOOKLIST[ LASTNAME(#PCDATA) > ]> Xml Document And Corresponding DTD

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) Allan 62 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

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 John 22 XPath: /Student[Name=“John”]/ Extracts: element with value

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: XML Document Database Row : XML Record

Examples John 120 Northwestern Ave Paul 120 N. Salisbury

Example Create table prTable(patientRecord XMLType); DECLARE prXML CLOB; BEGIN -- Store Patient Record XML in the CLOB variable prXML := ' John 120 Northwestern Ave ‘ ; -- 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, FROM prTable p; USE XPATH

Oracle JDBC JDBC an API used for database connectivity Creates Portable Applications Basic Steps to develop JDBC Application 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 = 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

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