Overview of JDBC and Pro*C 1 CSE 5330 – Database Systems

Overview of JDBC and Pro*C 2 Options for doing the project Windows application using Java – JDBC for database connectivity – Java AWT / Swing etc. for the GUI Menu driven program using Pro*C – If you know C, but not Java Web based application using CGI-Perl – Perl DBI module for database connectivity – CGI / HTML for the GUI Web based application using JSP, Java servlets, PHP etc. – Omega may not allow running some/all of these – Be prepared to demo on your own laptop etc.

Overview of JDBC and Pro*C 3 Java Database Connectivity (JDBC) JDBC provides a standardized library for accessing relational databases – Connecting to the database – Initiating queries – Creating stored (parameterized) queries – Data structure for the query result JDBC is not embedded SQL JDBC is located in java.sql package

Overview of JDBC and Pro*C 4 JDBC driver Java application JDBC driver manager JDBC API Oracle JDBC driver (classes12.zip) JDBC driver API Oracle database Client Server (omega)

Overview of JDBC and Pro*C 5 JDBC driver (continued) JDBC driver for Oracle needs to be on the client machine Available on omega at – /opt/oracle/product/ /jdbc/lib/classes12.zip The JDBC driver (classes12.zip) needs to be included in the runtime classpath

Overview of JDBC and Pro*C 6 Six steps in using JDBC 1.Load the driver 2.Establish a connection 3.Create a statement object 4.Execute a query 5.Process the results 6.Close the connection

Overview of JDBC and Pro*C 7 JDBC usage steps - details Step 1 : Load the driver try { Class.forName ("oracle.jdbc.driver.OracleDriver"); } catch(Exception e) { System.out.println("JDBC ORACLE driver failed to load"); }

Overview of JDBC and Pro*C 8 JDBC usage steps - details Step 2 : Establish a connection try { con = ta.edu:1521:CSE1"); } catch(Exception e) { System.out.println("Failed to connect to the database"); }

Overview of JDBC and Pro*C 9 JDBC usage steps - details Step 3 : Create a statement – Statement statement = con.createStatement(); Step 4 : Execute a query String query = “SELECT FNAME, SALARY FROM EMPLOYEE”; ResultSet rs = Statement.executeQuery(query); (For SELECT) String query = “UPDATE EMPLOYEE SET SALARY = WHERE FNAME = “John”; Statement.executeUpdate(query); (For UPDATE, INSERT, DELETE)

Overview of JDBC and Pro*C 10 JDBC usage steps - details Step 5 : Process the result While (rs.next()) { System.out.println(rs.getString(1) + “ “ + rs.getInt(2)); } First column has index 1, not 0 ResultSet provides various getXXX methods that take a column index, and return the data

Overview of JDBC and Pro*C 11 JDBC usage steps - details Step 6 : Close the connection – con.close(); As opening a connection is expensive, postpone this step if additional database operations are expected

Overview of JDBC and Pro*C 12 Online resources JDBC tutorial – JDBC API reference –

Overview of JDBC and Pro*C 13 Pro*C Embedded SQL – Allows you to embed SQL in C code Pro*C programC code Pre-compiler Executable C compiler Embedded SQL statementsSQL statements replaced By library calls SQLLIB Oracle runtime library

Overview of JDBC and Pro*C 14 Pro*C syntax SQL statements can be placed anywhere between a C block All SQL statements need to start with EXEC SQL and be terminated by a semicolon { int a; /*... */ EXEC SQL SELECT salary INTO :a FROM Employee WHERE SSN= ; /*... */ printf("The salary is %d\n", a); /*... */ } Be sure to include sqlca.h

Overview of JDBC and Pro*C 15 Connecting to the database Legal way char *username = "SCOTT"; char *password = "TIGER"; … EXEC SQL CONNECT :username IDENTIFIED BY :password; Illegal way – EXEC SQL CONNECT SCOTT IDENTIFIED BY TIGER; – EXEC SQL CONNECT 'SCOTT' IDENTIFIED BY 'TIGER';

Overview of JDBC and Pro*C 16 Dynamic sql Used to dynamically create entire SQL statements – char *s = "INSERT INTO emp VALUES(1234, 'jon', 3)"; – EXEC SQL PREPARE q FROM :s; – EXEC SQL EXECUTE q; Alternately, – char *s = "INSERT INTO emp VALUES(1234, 'jon', 3)"; – EXEC SQL EXECUTE IMMEDIATE :s;

Overview of JDBC and Pro*C 17 Host variables Key to the communication between the host program and the database They should be declared in a Declare section – EXEC SQL BEGIN DECLARE SECTION; – /* Declare all host variables inside this section: – */ char *uid = "scott/tiger"; –... – EXEC SQL END DECLARE SECTION;

Overview of JDBC and Pro*C 18 Transactions Sequence of SQL statements that are treated as a single unit of work Transaction ends when you issue – EXEC SQL COMMIT;

Overview of JDBC and Pro*C 19 Cursors Used for fetching multiple rows of data First, declare it. – EXEC SQL DECLARE emp_cursor CURSOR FOR – SELECT ename, empno, sal – FROM emp – WHERE deptno = :dept_number; Then, open it. – EXEC SQL OPEN emp_cursor; Fetch the records. – for (;;) – { – EXEC SQL FETCH emp_cursor INTO :emp_name1, :salary1; – }

Overview of JDBC and Pro*C 20 Cursors (continued) Finally, close it. – EXEC SQL CLOSE emp_cursor; Error handling – Every executable SQL statement returns a status code to the SQLCA variable sqlcode – A zero status code means that Oracle executed the statement without detecting an error or exception – A positive status code means that Oracle executed the statement but detected an exception – A negative status code means that Oracle did not execute the SQL statement because of an error.

Overview of JDBC and Pro*C 21 Pro*C set-up on omega All your Pro*C files should be named from lab1 to lab10 Use ‘make.proc labx’ to compile labx.pc This will precompile the.pc file to a C file, compile the C file and generate the executable for you Sample Pro*C program available. Run /home/a/ax/axs3919/lab2 /home/s/sh/sharmac/cse5330/spring2006/proC/lab2

Overview of JDBC and Pro*C 22 Online reference Pro*C/C++ Precompiler Programmer's Guide