ResultSet Cursor Initial Position: Before First Row

This section describes the ResultSet cursor initial position: before first row. next() should be called to move the cursor to the first row.

Right after the ResultSet object is returned from the executeQuery() call, the ResultSet cursor is positioned before the first row. You need to call next() once to move the cursor to the first row. If you missed this call, you will get an error message as shown by this sample program:

/* DerbyResultSetNoNext.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.sql.*;
public class DerbyResultSetNoNext {
  public static void main(String [] args) {
    Connection con = null;
    try {
      con = DriverManager.getConnection("jdbc:derby://localhost/TestDB");
      Statement sta = con.createStatement();

// Catch the ResultSet object
      ResultSet res = sta.executeQuery("SELECT * FROM Profile");

// Skip calling next()
//    res.next();

// Try to get column values
      String firstName = res.getString("FirstName");
      String lastName = res.getString("LastName");

// Close ResultSet
      res.close();

      sta.close();
      con.close();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
    }
  }
}

Run this program to see the error if res.next() is not called after executeQuery():

Exception: Invalid operation at current cursor position.

Table of Contents

 About This Book

 JDBC (Java Database Connectivity) Introduction

 JDK (Java SE) Installation

 Installing and Running Java DB - Derby

 Derby (Java DB) JDBC Driver

 Derby (Java DB) JDBC DataSource Objects

 Java DB (Derby) - DML Statements

Java DB (Derby) - ResultSet Objects of Queries

 What Is ResultSet?

 ResultSet Cursor and Scrollability

ResultSet Cursor Initial Position: Before First Row

 Retrieving Column Values with getXXX() Methods

 ResultSet Default Type: Forward-only

 Scrollable ResultSet and Moving Cursor Backward

 ResultSet Objects with Update Capability

 insertRow() - Inserting New Rows through ResultSet Objects

 updateXXX() - Updating Column Values for Row Update or Insert

 deleteRow() - Deleting Rows through ResultSet Objects

 Java DB (Derby) - PreparedStatement

 Summary of JDBC Drivers and Database Servers

 Using Connection Pool with JDBC

 Archived Tutorials

 References

 Full Version in PDF/EPUB