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Delete a Column from a Database Table

                         

In this section, we are going to learn how to delete a column from a database table. We are not going to create a new table into, and we are expecting that you can make a table yourself. We are using the already created table in the specific database. Now if we want to delete a column from a database table then we have been provided with the  database query by which we can do this task very easily. See detailed information  below:

Description of program:

The thing which we are going to perform first is to establish the connection by using the JDBC driver. If any problem is created at the time of connection then it shows java.lang.ClassNotFoundException exception. After establishing the connection gives a table name and column name which you want to delete. When column gets deleted then it shows "Column is deleted successfully". But if SQL statement doesn't get executed then an exception is thrown and displays a message: "Table or column is not found!".

Description of code:

ALTER TABLE    table_name    DROP   col_name;
This code is used to delete the column form a database table 
        table_name: This is a table name in which you want to any editing.
        col_name: This is a column name which have to deleted.

Here is the code of program:

import java.io.*;
import java.sql.*;

public class DeleteColumn{
  public static void main(String[] args) {
    System.out.println("Delete columns 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();
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter table name: ");
        String table = bf.readLine();
        System.out.println("Enter column name: ");
        String col = bf.readLine();
        st.executeUpdate("ALTER TABLE "+table+" DROP "+col);
        System.out.println("Column is deleted successfully!");
      }
      catch (SQLException s){
        System.out.println("Table or column is not found!");
      }
    }
    catch (Exception e){
      e.printStackTrace();
    }
  }
}

Database Table: Student Table

Stu_roll Stu_name Stu_sub Stu_marks
100 vinod computer 95
101 raju math 89
102 ranjan bio 80
103 Aman phy 85

Output of program:

C:\vinod\jdbc\jdbc\jdbc-mysql>javac DeleteColumn.java

C:\vinod\jdbc\jdbc\jdbc-mysql>java DeleteColumn
Delete columns example!
Enter table name:
Student
Enter column name:
Stu_marks
Column is deleted successfully!

After deleting a column: 

Student Table

Stu_roll Stu_name Stu_sub
100 vinod computer
101 raju math
102 ranjan bio
103 Aman phy

Download this example.

                         

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