ResultSet

In JDBC, the ResultSet interface represents the result set of a query. It provides methods to read data returned by a query, typically from a SELECT statement. A ResultSet is created by executing a query using the Statement or PreparedStatement objects, and it allows navigation and extraction of data from the result.

Types of ResultSet

  1. Forward-only:

    • This is the default type, where you can only move the cursor forward through the result set.
    • Created with: Statement statement = conn.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);

  2. Scrollable:

    • Allows navigation in both directions, forward and backward, through the result set.
    • Created with: Statement statement = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);

  3. Updatable:

    • Allows updating the values in the result set.
    • Created with: Statement statement = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);

Common Methods of ResultSet

  • next(): Moves the cursor to the next row in the result set.

    while (rs.next()) {
    System.out.println(rs.getString("name"));
}


* **getString()**: Retrieves a column value as a `String`.

  ```java
  String name = rs.getString("name");

  • getInt(): Retrieves a column value as an int.

    int id = rs.getInt("id");

  • getBoolean(): Retrieves a column value as a boolean.

    boolean isActive = rs.getBoolean("is_active");

  • getDate(): Retrieves a column value as a Date.

    Date birthDate = rs.getDate("birth_date");

Example: Using ResultSet to Process Query Results

import java.sql.*;

public class ResultSetExample {
    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "root", "password");
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT id, name, age FROM users");

            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
            }

            rs.close();
            stmt.close();
            conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

🔗 Related Notes