Wednesday, 1 July 2020

Java ResultSet next() method with example

Java ResultSet next() method with example

When we execute certain SQL queries (SELECT query in general) they return tabular data.
The java.sql.ResultSet interface represents such tabular data returned by the SQL statements.
i.e. the ResultSet object holds the tabular data returned by the methods that execute the statements which quires the database (executeQuery() method of the Statement interface in general).

The ResultSet object has a cursor/pointer which points to the current row. Initially this cursor is positioned before first row.The next() method of the ResultSet interface moves the pointer of the current (ResultSet) object to the next row, from the current position.

Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from MyPlayers");
rs.next();
i.e., on calling the next() method for the first time the result set pointer/cursor will be moved to the 1st row (from default position).And on calling the next() method for the second time the result set cursor will be moved to the 2nd row.Return value
This method returns a boolean value specifying whether the ResultSet object contains more rows.

If there are no rows next to its current position this method returns false, else it returns true.

Using this method in the while loop you can iterate the contents of the result set.

while(rs.next()){
   System.out.println(rs.getString(1));
   System.out.println(rs.getString(2));
}
Example
Let us create a table with name MyPlayers in MySQL database using CREATE statement as shown below -

CREATE TABLE MyPlayers(
   ID INT,
   First_Name VARCHAR(255),
   Last_Name VARCHAR(255),
   Date_Of_Birth date,
   Place_Of_Birth VARCHAR(255),
   Country VARCHAR(255),
   PRIMARY KEY (ID)
);
Now, we will insert 7 records in MyPlayers table using INSERT statements -

insert into MyPlayers values(1, 'Shikhar', 'Dhawan', DATE('1981-12-05'), 'Delhi', 'India');
insert into MyPlayers values(2, 'Jonathan', 'Trott', DATE('1981-04-22'), 'CapeTown', 'SouthAfrica');
insert into MyPlayers values(3, 'Kumara', 'Sangakkara', DATE('1977-10-27'), 'Matale', 'Srilanka');
insert into MyPlayers values(4, 'Virat', 'Kohli', DATE('1988-11-05'), 'Delhi', 'India');
insert into MyPlayers values(5, 'Rohit', 'Sharma', DATE('1987-04-30'), 'Nagpur', 'India');
insert into MyPlayers values(6, 'Ravindra', 'Jadeja', DATE('1988-12-06'), 'Nagpur', 'India');
insert into MyPlayers values(7, 'James', 'Anderson', DATE('1982-06-30'), 'Burnley', 'England');
Following JDBC program establishes connection with the database, retrieves the contents of the table MyPlayers into a ResultSet object, moves the cursor to the next row thrice using the next() method and prints the contents of the row at each position.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class ResultSet_next {
   public static void main(String args[]) throws SQLException {
      //Registering the Driver
      DriverManager.registerDriver(new com.mysql.jdbc.Driver());
      //Getting the connection
      String mysqlUrl = "jdbc:mysql://localhost/mydatabase";
      Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
      System.out.println("Connection established......");
      //Creating the Statement
      Statement stmt = con.createStatement();
      //Query to retrieve records
      String query = "Select * from MyPlayers";
      //Executing the query
      ResultSet rs = stmt.executeQuery(query);
      System.out.println("Contents of the first record: ");
      //Moving the cursor from default position to 1st row.
      rs.next();
      //Current record details.
      System.out.print("ID: "+rs.getInt("ID")+", ");
      System.out.print("Name: "+rs.getString("First_Name")+", ");
      System.out.print("Age: "+rs.getString("Last_Name")+", ");
      System.out.print("Salary: "+rs.getDate("Date_Of_Birth")+", ");
      System.out.print("Country: "+rs.getString("Place_Of_Birth")+", ");
      System.out.print("Address: "+rs.getString("Country"));
      System.out.println();
      //Moving the cursor from default position to 1st row.
      rs.next();
      //Current record details.
      System.out.print("ID: "+rs.getInt("ID")+", ");
      System.out.print("Name: "+rs.getString("First_Name")+", ");
      System.out.print("Age: "+rs.getString("Last_Name")+", ");
      System.out.print("Salary: "+rs.getDate("Date_Of_Birth")+", ");
      System.out.print("Country: "+rs.getString("Place_Of_Birth")+", ");
      System.out.print("Address: "+rs.getString("Country"));
      System.out.println();
      //Moving the cursor from 1st row position to 2nd row.
      rs.next();
      //Current record details.
      System.out.print("ID: "+rs.getInt("ID")+", ");
      System.out.print("Name: "+rs.getString("First_Name")+", ");
      System.out.print("Age: "+rs.getString("Last_Name")+", ");
      System.out.print("Salary: "+rs.getDate("Date_Of_Birth")+", ");
      System.out.print("Country: "+rs.getString("Place_Of_Birth")+", ");
      System.out.print("Address: "+rs.getString("Country"));
      System.out.println();
      //Moving the cursor from 2nd row to 3rd row.
      rs.next();
      //Current record details.
      System.out.print("ID: "+rs.getInt("ID")+", ");
      System.out.print("Name: "+rs.getString("First_Name")+", ");
      System.out.print("Age: "+rs.getString("Last_Name")+", ");
      System.out.print("Salary: "+rs.getDate("Date_Of_Birth")+", ");
      System.out.print("Country: "+rs.getString("Place_Of_Birth")+", ");
      System.out.print("Address: "+rs.getString("Country"));
      System.out.println();
   }
}

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