ResultSet interface

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The ResultSet interface is a part of the Java Database Connectivity (JDBC) API, which provides a set of Java classes for accessing and manipulating databases. The ResultSet interface provides methods for accessing and processing the results of a database query.

When a Statement object is executed using a database query, it returns a ResultSet object, which contains the results of the query. The ResultSet object maintains a cursor that points to the current row of data in the result set. The cursor can be moved to navigate through the rows of the result set, and the data in each row can be retrieved using the appropriate methods.

The ResultSet interface provides methods for retrieving data from the result set based on the data type of the column, such as getInt(), getString(), getDouble(), and so on. It also provides methods for navigating through the result set, such as next(), previous(), first(), last(), and so on.

In addition, the ResultSet interface provides methods for updating and deleting rows in the result set, such as updateRow(), deleteRow(), and so on. However, not all databases support these methods, and the behavior of these methods may vary depending on the database driver.

Overall, the ResultSet interface provides a powerful mechanism for retrieving and processing data from a database using Java.

Commonly used methods of ResultSet interface:

Here are some commonly used methods of the ResultSet interface in Java:

  1. next(): Moves the cursor to the next row in the result set.
  2. getInt(int columnIndex): Returns the value of the specified column as an int in the current row of the result set.
  3. getString(int columnIndex): Returns the value of the specified column as a String in the current row of the result set.
  4. getDouble(int columnIndex): Returns the value of the specified column as a double in the current row of the result set.
  5. getDate(int columnIndex): Returns the value of the specified column as a java.sql.Date object in the current row of the result set.
  6. getTime(int columnIndex): Returns the value of the specified column as a java.sql.Time object in the current row of the result set.
  7. getTimestamp(int columnIndex): Returns the value of the specified column as a java.sql.Timestamp object in the current row of the result set.
  8. beforeFirst(): Moves the cursor to before the first row in the result set.
  9. afterLast(): Moves the cursor to after the last row in the result set.
  10. first(): Moves the cursor to the first row in the result set.
  11. last(): Moves the cursor to the last row in the result set.
  12. absolute(int row): Moves the cursor to the specified row number in the result set.
  13. updateRow(): Updates the current row in the result set with the changes made using updateX() methods.
  14. deleteRow(): Deletes the current row from the result set.
  15. close(): Releases any resources held by the ResultSet object.

These methods provide a powerful mechanism for retrieving and processing data from a database using Java.

Example of Scrollable ResultSet:

A Scrollable ResultSet allows you to move the cursor to any row in the result set, not just the next row. You can move the cursor forward and backward through the result set, or jump directly to a specific row. Here’s an example of using a Scrollable ResultSet in Java:

import java.sql.*;

public class ScrollableResultSetExample {

    public static void main(String[] args) throws SQLException {
        
        String url = "jdbc:mysql://localhost:3306/mydb";
        String user = "root";
        String password = "mypassword";
        
        Connection connection = DriverManager.getConnection(url, user, password);
        
        Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
        ResultSet resultSet = statement.executeQuery("SELECT * FROM users");
        
        // Move the cursor to the first row
        resultSet.first();
        
        // Print the data in the first row
        System.out.println(resultSet.getString("name") + " - " + resultSet.getString("email"));
        
        // Move the cursor to the third row
        resultSet.absolute(3);
        
        // Print the data in the third row
        System.out.println(resultSet.getString("name") + " - " + resultSet.getString("email"));
        
        // Move the cursor to the last row
        resultSet.last();
        
        // Print the data in the last row
        System.out.println(resultSet.getString("name") + " - " + resultSet.getString("email"));
        
        // Move the cursor to the second-to-last row
        resultSet.previous();
        
        // Print the data in the second-to-last row
        System.out.println(resultSet.getString("name") + " - " + resultSet.getString("email"));
        
        // Close the ResultSet, Statement, and Connection objects
        resultSet.close();
        statement.close();
        connection.close();
    }
}

In this example, we use a Scrollable ResultSet by passing ResultSet.TYPE_SCROLL_INSENSITIVE and ResultSet.CONCUR_READ_ONLY as arguments to the createStatement() method. We then move the cursor to different rows in the result set using methods like first(), absolute(), last(), and previous(). Finally, we close the ResultSet, Statement, and Connection objects to release any resources held by them.