Cross Join Tables in a Specific Database
This section introduces you to the cross join between two
tables. The cross join operation retrieves data between two tables as a Cartesian
product of set theory in mathematics. Each row will get multiplied by other
rows. If one table has three rows and the second row has two rows, then the
cartesian of two table will be six. See brief description below:
Cross Join: This is a type of join table
operation. It is a same as inner and outer join operation. The
cross join is used to retrieve data from tables as Cartesian product format of
set theory in mathematics. All rows are shown to be multiply by to another
tables' rows.
Description of program:
First of all this program establishes the connection,
after that the cross join operation will be performed between two tables. Both tables hold
some specific fields and it's values. While you retrieve data in cross join
format, it shows that the each row will get multiply by other rows.
Description of code:
SELECT *FROM employee, Emp_sal :
This code is used to retrieve data form both tables as Cartesian product
format (multiply the field to each other).
Here is the code of program:
import java.sql.*;
public class CrossJoinTable{
public static void main(String[] args) {
System.out.println("Natural Left Join Tables Example!");
Connection con = null;
try{
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection
("jdbc:mysql://localhost:3306/jdbctutorial","root","root");
try{
Statement st = con.createStatement();
ResultSet res = st.executeQuery
("SELECT *FROM "+"employee"+","+"Emp_sal"); //Cross Join two tables
System.out.println("Emp_name" + "\t" + "Emp_ed" + "\t" + "Emp_sal");
while(res.next()){
String name = res.getString("Emp_name");
int ed = res.getInt("Emp_ed");
int sal = res.getInt("Emp_sal");
System.out.println(name + "\t\t" + ed + "\t" + sal);
}
}
catch (SQLException s){
System.out.println("SQL statement is not executed!");
}
}
catch (Exception e){
e.printStackTrace();
}
}
}
|
Download this example.
Table:-
employee:
| Emp_ed |
Emp_name |
| 2
10
13 |
santosh
deepak
Aman |
Table:- Emp_sal:
| Emp_name |
Emp_sal |
| Aman
santosh |
8000
4500 |
Output of program:
C:\vinod\jdbc\jdbc\jdbc-mysql>javac CrossJoinTable.java
C:\vinod\jdbc\jdbc\jdbc-mysql>java CrossJoinTable
Natural Left Join Tables Example!
Emp_name Emp_ed
Emp_sal
santosh 2
8000
santosh 2
4500
deepak 10
8000
deepak 10
4500
Aman 13
8000
Aman 13
4500 |
|
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