数据库系统原理PPT.7z

/**********************************************************************/ /* labposition.java */ /* Sample Java program for "DB2 UDB PROGRAMMING USING JAVA" */ /* ( CG11 ) */ /* */ /* Learn how to establish in position in a ResultSet */ /* */ /* */ /* Last update = 01/31/2000 */ /* */ /**********************************************************************/ /* Notes: */ /* */ /* This program is intended to be completed with the lab guide */ /* as a reference. The lab guide is the set of instructions that */ /* should be followed. The comments in this program are intended */ /* to clarify statements made in the lab guide. */ /**********************************************************************/ /**********************************************************************/ /* Import Java Classes */ /**********************************************************************/ import java.sql.*; import sqlj.runtime.*; import sqlj.runtime.ref.*; import java.io.*; import java.util.*; import java.math.*; /**********************************************************************/ /* Class definition */ /**********************************************************************/ public class labposition { /**********************************************************************/ /* Register the class with the db2 Driver */ /**********************************************************************/ static { try { Class.forName ("COM.ibm.db2.jdbc.app.DB2Driver"); } catch (Exception e) { System.out.println ("\n Error loading DB2 Driver...\n"); System.out.println (e); System.exit(1); } } /**********************************************************************/ /* Main routine */ /**********************************************************************/ public static void main( String args[]) throws Exception { /**********************************************************************/ /* Define variable declarations for the variable which will be used */ /* to pass data to and from the stored procedure: */ /* A character string for passing the department in. */ /* A double for returning the median salary. */ /* An integer for returning the number of employees. */ /**********************************************************************/ String name = ""; java.lang.String deptno = ""; short id = 0; String salary = ""; String job = ""; short NumEmp = 0; BufferedReader in = new BufferedReader( new InputStreamReader (System.in)); String s; /***********************************************************************/ /* Header line */ /***********************************************************************/ String intext = "\n NAME JOB SALARY\n"; String indash = "-------- -------- --------------\n"; String blanks = " "; String outline = ""; /* Establish connection and set default context */ System.out.println("Connect statement follows:"); /********************* ???????????????? ************************/ /* ( 1 ) Code the connect statement to the database SAMPLE */ /* use the Connection object named sample. */ /***************************************************************/ Connection sample = DriverManager.getConnection("jdbc:db2:sample","udba","udba"); System.out.println("Connect completed"); sample.setAutoCommit(false); /* Issue Select statement */ System.out.println("Statement stmt follows"); try { /************************ ?????????????????????? ***********************/ /* Execute the statement SELECT * FROM STAFF */ /* */ /* Print out the results by filling in the appropriate variable */ /* names in each of the following println invocations. */ /***********************************************************************/ /************************** ???????????????????? ***********************/ /* ( 2 ) Define the ResultSet object named rs. */ /* Initialize the rs object to null. */ /***********************************************************************/ ResultSet rs = null; /************************** ???????????????????? ***********************/ /* ( 3 ) Define the variable sql which contain the select statement */ /* SELECT NAME, JOB, SALARY FROM STAFF */ /***********************************************************************/ String sql = "select NAME, JOB, SALARY from staff "; /************************** ???????????????????? ***********************/ /* ( 4 ) Instantiate the PreparedStatement object stmt. */ /* Make the cursor allow for scrollable backward and forward */ /***********************************************************************/ PreparedStatement stmt = sample.prepareStatement(sql, rs.TYPE_SCROLL_INSENSITIVE, rs.CONCUR_READ_ONLY); System.out.println( intext ); System.out.println( indash ); rs = stmt.executeQuery( ); /************************** ???????????????????? ***********************/ /* ( 5 ) Scrollforward through the result set. */ /* */ /***********************************************************************/ rs.next(); name = rs.getString(1); job = rs.getString(2); salary = rs.getString(3); outline = (name + blanks.substring(0, 10 - name.length())) + (job + blanks.substring(0, 10 - job.length())) + (salary + blanks.substring(0, 12 - salary.length())); System.out.println("\n" + outline); /************************** ???????????????????? ***********************/ /* ( 6 ) Retrieve the last row of the result set */ /* */ /***********************************************************************/ rs.last(); name = rs.getString(1); job = rs.getString(2); salary = rs.getString(3); outline = (name + blanks.substring(0, 10 - name.length())) + (job + blanks.substring(0, 10 - job.length())) + (salary + blanks.substring(0, 12 - salary.length())); System.out.println("\n" + outline); /************************** ???????????????????? ***********************/ /* ( 7 )