Natural left join

Natural left join

Posted in : Core Java Posted on : October 18, 2010 at 6:26 PM Comments : [ 0 ]

This section contains the detail about the Natural left join in java.

Natural left join

In Natural Left join, both table are merge to each other according to common field, but the priority is given to the first table's field values  means a left outer join returns all the values from the left table and matched values from the right table (NULL in case of no matching join predicate).

In left join, every row of left table appears at least once in joined table, If no matching row from the "right" table exists, NULL will appear in columns from Right Table for those records that have no match in Left Table.

Query for Left Join


The two tables before Left join --

"employee" table

"emp_sal" table

import java.sql.*;

public class natleftjoin{
public static void main(String[] args) {
System.out.println("NATURAL LEFT JOIN");
Connection con = null;
con = DriverManager.getConnection("jdbc:mysql://","root","root");
Statement st = con.createStatement();
ResultSet res = st.executeQuery("SELECT *FROM "+"employee"+" NATURAL LEFT JOIN "+"emp_sal");
		 //Natural Left Join two tables
System.out.println("Emp_code" + "\t" + "Emp_name" + "\t" + "Emp_salary"+"\t"+"Emp_designation");
int code = res.getInt("Emp_code");
String name = res.getString("Emp_name");
String sal = res.getString("Emp_salary");
String post = res.getString("Emp_designation");

System.out.println(code + "\t\t" + name + "\t\t" + sal+"\t\t"+post);
catch (SQLException s){
System.out.println("SQL statement is not executed!");
catch (Exception e){

Output :

Download Source Code

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