java03_main.java

Hierarchy. Same as 02_java but with three tables.

import java.sql.*;
 
public class java03_main {
 
/*
                                                    
     *  EXAMPLE - 03_java for JDBC
                                                    
     * When you run this example, a new database is created with three tables
                                                    
     * in a hierarchy where one references another, which references the third
                                                    
     * one.  Then a single row is created in the top table and three rows are
                                                    
     * created in the middle table and nine rows in the bottom table.
                                                    
     * Finally all the data is read from the database using a join.
                                                    
     * 
                                                    
     * Full documentation for RDM is available at http://docs.raima.com/rdm/
                                                    
     * 
                                                    
     * For simplicity this example utilizes basic exception handling
                                                    
     * but good programming practices would dictate that this occur in 
                                                    
     * a full application.
                                                    
     */
                                                    
public static void main(String[] args) throws SQLException  {
 
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

                                                    
try
                                                    
        {
/* Create the connection with a simple connection string */
                                                    
            conn = DriverManager.getConnection("jdbc:raima:rdm://local");
            conn.setAutoCommit(true);

                                                    
            CreateDatabase(conn);

                                                    
/* Open the connection to the database */
                                                    
            stmt = conn.createStatement();

                                                    
/* Insert a row into the top table */
                                                    
            stmt.executeUpdate("INSERT INTO TopTab VALUES 1, 'top 1'");

                                                    
/* Insert three rows into the middle table */
                                                    
for (int ii = 1; ii < 5; ii++)
            {
                stmt.executeUpdate("INSERT INTO MidTab VALUES " + ii + ", 'mid " + ii +"', 1");
for (int jj = 1; jj < 4; jj++)
                {
                    stmt.executeUpdate("INSERT INTO BotTab VALUES 'bot " + ((ii - 1) * 3 + jj) + "', " + ii);
                }
            }

                                                    
/* Scan through all the existing rows using a join and display the contents */
                                                    
            rs = stmt.executeQuery("SELECT tstr, mstr, bstr FROM TopTab, MidTab, BotTab WHERE TopTab.tid = MidTab.tid AND MidTab.mid = BotTab.mid");
while (rs.next() != false)
            {
                System.out.println(rs.getString(1) + " -- " + rs.getString(2) + " -- " + rs.getString(3));
            }
        }
catch (SQLException sqle)
        {
            sqle.printStackTrace();
        }
finally
                                                    
        {
if(rs != null)
                rs.close();
 
if(stmt != null)
                stmt.close();

                                                    
if(conn != null)
                conn.close();           
        }
    }

                                                    
private static void CreateDatabase(Connection conn)
    {
        Statement stmt = null;

                                                    
try
                                                    
        {
/* Create the example database */
                                                    
            stmt = conn.createStatement();
/* Since the database is created here, it cannot be created twice */
                                                    
try {
                stmt.executeUpdate("DROP DATABASE java03");
            } catch (SQLException sqle) {}

                                                    
            stmt.execute("CREATE DATABASE java03");
            stmt.execute("CREATE TABLE TopTab (tid INTEGER PRIMARY KEY, tstr CHAR(30))");
            stmt.execute("CREATE TABLE MidTab (mid INTEGER PRIMARY KEY, mstr CHAR(30), tid INTEGER REFERENCES TopTab(tid))");
            stmt.execute("CREATE TABLE BotTab (bstr CHAR(30), mid INTEGER REFERENCES MidTab(mid))");
            conn.commit();
            stmt.close();
            stmt = null;
        }
catch (SQLException sqle)
        {
            sqle.printStackTrace();
        }
    }       
}