private void initJDBC ()
{
  try{
    class.forName("oracle.jdbc.driver.OracleDriver".newInstance();
                 String dwUrl = "jdbcracle:thin:@skull:1521:HERO";
    connDW = DriverManager.getConnection(dwUrl, "scott", "tiger";
// define SQL commands
   String sqlInsert = "INSERT INTO Quarterly_Sales "
                  + " (Region_ID, Store_ID, Year, "
                  +  " Quarter, Sales) "
                    +  " VALUES (?, ?, ?, ?, ?)";
   String sqlUpdate = "UPDATE Quarterly_Sales "
                  + " SET Sales = Sales + ? "
                  + "WHERE Region_ID = ? "
                    +  " AND Store_ID = ? "
                  +  " AND Year = ?"
                  +  " AND Quarter = ?";
// prepare statements
   psInsert = connDW.prepareStatement (sqlInsert);
   psUpdate = connDW.prepareStatement (sqlUpdate);
  } catch (Exception e)
  {  System.out.println ("Error initializing JDBC connection";
         e.printStackTrace();
  }
}

private void addToUpdate (String region, String store, String year,String quarter, String amount)
{
  try
  {
// first try to update existing quarter
   psUpdate.clearParameters();
   psUpdate.setString (1, amount);
   psUpdate.setString (2, region);
   psUpdate.setString (3, store);
   psUpdate.setString (4, year);
   psUpdate.setString (5, quarter);
   int n = psUpdate.executeUpdate();
   System.out.println(n);
}catch (Exception e)
  {  System.out.println ("Error Updating to database";
     e.printStackTrace();
  }
}

private void addToInsert (String region, String store, String year,String quarter, String amount)
{
// if no updates, add new quarter
   try{
         psInsert.clearParameters();
         psInsert.setString (1, region);
         psInsert.setString (2, store);
         psInsert.setString (3, year);
         psInsert.setString (4, quarter);
         psInsert.setString (5, amount);
         psInsert.executeUpdate();
         nInsert++;
   }catch (Exception e)
     {  System.out.println ("Error writing to database";
        e.printStackTrace();
      }
}

public static void main(String[] args){
    Edit3   test = new Edit3();
    test.initJDBC();
    test.addToInsert("02", "10", "2003" , "01", "10";
    test.addToUpdate("02", "10", "2003" , "01", "30";
    test.addToInsert("02", "10", "2003" , "02", "10";          
   test.closeJDBC();
}

~~~~~~~~~~~~~~~~~~~~~~
数据字典
   region, store, year, quarter,    salse
     char    char  char    char    numeric(8,3)
照理说结果是
   region, store, year, quarter, amount
     __02 __10___2003___01___40
     __02 __10___2003___02___10
可是test.addToUpdate("02", "10", "2003" , "01", "30";却不成功。
现在错误的结果是
   region, store, year, quarter, amount
     __02__10___2003___01___10
     __02__10___2003___02___10

请问是什么道理啊？问题是不是出在update Quarterly_Sales SET sale= sale + ? (amount)上啊？

建议你一句一句调试，找出问题。
这个论坛使用Java编程人的不多。

问题找出来了
应该是oracle，sql本身，呵呵

region, store, year, quarter都使用char的，所以在where中要用trim()去掉额外空格。