Join tables in the specific database

In this section, we are going to see how to join two or more tables in a specific database.

Join tables in the specific database

Join tables in the specific database

     

Consider a case, where there is too many records and tables in a database. Now to retrieve a particular row from a table or database is a very time consuming. So, what the alternative to that, divide the table in more than one table. In this section, we are going to see how to join two or more tables in a specific database. For this you need to have two or more table in the database. If two or more tables are available in the database then Join operation is performed otherwise not. Firstly, it is important to know about the join operation. Join operation provides the facility to combine records between two or more tables. It relates one table to another. Joining is the type of query for retrieving data two or more table in specific database. You can join the tables various types like: Natural join, Natural left join, Natural right join and so on. Here we are providing you an example with code that joins two tables through the NATURAL JOIN. Brief information given below:

Join: A join provides the facility to connect two tables are merged to each other according to field that is common and creates a new virtual table.

NATURAL JOIN: It is a type of join that retrieves data within specified tables to specific field is matched.

NATURAL LEFT JOIN: In this operation both tables are merged to each other according to common fields but the priority is given to the first table in database.

NATURAL RIGHT JOIN: It also same as Natural left join but it retrieves the data from the second table in the database.

Description of program:

First of all, this program establishes the connection with MySQL database through the JDBC driver. After establishing the connection the NATURAL JOIN operation is performed within two tables say: employee and Emp_sal. The employee table holds the Emp_ed and Emp_name fields and Emp_sal table contains the Emp_name and Emp_sal. We are making use of the emp_name to join the tables.

Description of code:

SELECT *FROM employee NATURAL JOIN Emp_sal:
This code is used to show all fields that matches in the both tables on the basis of Emp_name field.

Here is the code of program:

import java.sql.*;

public class NatJoinTable{
  public static void main(String[] args) {
  System.out.println("Natural 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"+" NATURAL JOIN "+"Emp_sal");  //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 NatJoinTable.java

C:\vinod\jdbc\jdbc\jdbc-mysql>java NatJoinTable
Natural Join Tables Example!
Emp_name   Emp_ed   Emp_sal
santosh  2  4500
Aman   13   8000

Tutorials

  1. Mapping MySQL Data Types in Java
  2. Connecting to a MySQL Database in Java
  3. Creating a Database in MySQL
  4. Creating a Database Table
  5. Creating a MySQL Database Table to store Java Types
  6. Description of Database Table
  7. Deleting a Table from Database
  8. Retrieving Tables from a Database
  9. Inserting values in MySQL database table
  10. Retrieving All Rows from a Database Table
  11. Adding a New Column Name in Database Table
  12. Change Column Name of a Table
  13. Make Unique Column in Database Table
  14. Remove Unique Column in Database Table
  15. Arrange a Column of Database Table
  16. Arrange a Column of Database Table
  17. Sum of Column in a Database Table
  18. Deleting All Rows from a Database Table
  19. Delete a Specific Row from a Database Table
  20. Delete a Column from a Database Table
  21. Join tables in the specific database
  22. Join tables with the NATURAL LEFT JOIN operation
  23. Join tables with the NATURAL RIGHT JOIN operation
  24. Cross Join Tables in a Specific Database
  25. Prepared Statement Set Object
  26. Statement Batch Update
  27. Prepared Statement With Batch Update
  28. Select Records Using Prepared Statement
  29. Update Records using Prepared Statement
  30. Inserting Records using the Prepared Statement
  31. Count Records using the Prepared Statement
  32. Deleting Records using the Prepared Statement
  33. Using the Prepared Statement Twice
  34. Set Data Types by using Prepared Statement
  35. Set byte, short and long data types by using the Prepared Statement
  36. Prepared Statement Set Big Decimal
  37. Set Date by using the Prepared Statement
  38. Set Time by using the Prepared Statement
  39. Set Timestamp by using the Prepared Statement
  40. Copy Table in a MySQL Database