There are two types of result sets namely, forward only and, bidirectional.
Forward only ResultSet: The ResultSet object whose cursor moves only in one direction is known as forward only ResultSet. By default, JDBC result sets are forward-only result sets.
You can move the cursor of the forward only ResultSets using the next() method of the ResultSet interface. It moves the pointer to the next row from the current position. This method returns a boolean value. If there are no rows next to its current position it returns false, else it returns true.
Therefore, using this method in the while loop you can iterate the contents of the ResultSet object.
while(rs.next()){
}Example
Assume we have a table named dataset with content as shown below:
+--------------+-----------+ | mobile_brand | unit_sale | +--------------+-----------+ | Iphone | 3000 | | Samsung | 4000 | | Nokia | 5000 | | Vivo | 1500 | +--------------+-----------+
The following example retrieves all the records of the Dataset table and prints the results:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class RetrievingData {
public static void main(String args[]) throws Exception {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql://localhost/TestDB";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating a Statement object
Statement stmt = con.createStatement();
//Retrieving the data
ResultSet rs = stmt.executeQuery("select * from Dataset");
System.out.println("Contents of the table");
while(rs.next()) {
System.out.print("Brand: "+rs.getString("Mobile_Brand")+", ");
System.out.print("Sale: "+rs.getString("Unit_Sale"));
System.out.println("");
}
}
}Output
Connection established...... Contents of the table Brand: Iphone, Sale: 3000 Brand: Samsung, Sale: 4000 Brand: Nokia, Sale: 5000 Brand: Vivo, Sale: 1500
Bidirectional ResultSet: A bi-directional ResultSet object is the one whose cursor moves in both forward and backward directions.
The createStatement() method of the Connection interface has a variant which accepts two integer values representing the result set type and the concurrency type.
Statement createStatement(int resultSetType, int resultSetConcurrency)
To create a bi-directional result set you need to pass the type as ResultSet.TYPE_SCROLL_SENSITIVE or ResultSet.TYPE_SCROLL_INSENSITIVE, along with the concurrency, to this method as:
//Creating a Statement object Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
Example
Following example demonstrates the creation of bi-directional ResultSet. Here we trying to created a bi-directional ResultSet object which retrieves the data from the table name dataset and, we are trying to print rows of the dataset table from last to first using the previous() method.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class BidirectionalResultSet {
public static void main(String args[]) throws Exception {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String mysqlUrl = "jdbc:mysql://localhost/TestDB";
Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
System.out.println("Connection established......");
//Creating a Statement object
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_UPDATABLE);
//Retrieving the data
ResultSet rs = stmt.executeQuery("select * from Dataset");
rs.afterLast();
System.out.println("Contents of the table");
while(rs.previous()) {
System.out.print("Brand: "+rs.getString("Mobile_Brand")+", ");
System.out.print("Sale: "+rs.getString("Unit_Sale"));
System.out.println("");
}
}
}Output
Connection established...... Contents of the table Brand: Vivo, Sale: 1500 Brand: Nokia, Sale: 5000 Brand: Samsung, Sale: 4000 Brand: IPhone, Sale: 3000